The validity and reliability of the diagnosis of hyperkinetic disorders in the Danish Psychiatric Central Research Registry

Validation of anorexia nervosa and Bulimia nervosa diagnosis coding in Danish hospitals assisted by a natural language processing model

INTRODUCTION

The Danish Health Care Registers rely on the International Statistical Classification of Diseases and Related Health Problems (ICD)-classification and stand as a widely utilized resource for health epidemiological research. Eating disorders are multifaceted syndromes where two distinctive diagnoses are defined, anorexia nervosa (AN) and bulimia nervosa (BN). However, the validity of the registered diagnoses remains to be verified. Manuel chart review is often the method for validation of diagnosis codes, but there is limited research on how natural language processing (NLP) models could enhance this process.

OBJECTIVE

To investigate the accuracy of the clinical use of ICD-10 diagnosis codes F50.0, F50.1, F50.2, and F50.3 in the Danish Health Care Registers, using a manual chart review assisted by NLP.

METHOD

From a cohort of all individuals attending hospitals in Region of Southern Denmark with registered electronic health information, we extracted medical information from the electronic health journal on 100 individuals with each of the four diagnosis codes. After extraction, an NLP model with regular expression search patterns identified relevant text passages for manual chart review.

RESULTS

Overall, 372 of the 400 diagnosis codes (93%) were correct. A diagnosis code for AN was correct in 90% of instances, 96% for atypical AN, 96% for BN and 90% for an atypical BN diagnosis code.

CONCLUSION

We found that the accuracy of a diagnosis code F50.0, F50.1, F50.2, and F50.3 to be high. This confirms that the generally well-documented validity of the Danish health care registers also applies to the eating disorder diagnoses.

The role of co-occurring conditions and genetics in the associations of eating disorders with attention-deficit/hyperactivity disorder and autism spectrum disorder

Eating disorders (EDs) commonly co-occur with other psychiatric and neurodevelopmental disorders including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD); however, the pattern of family history and genetic overlap among them requires clarification. This study investigated the diagnostic, familial, and genetic associations of EDs with ADHD and ASD. The nationwide population-based cohort study included all individuals born in Denmark, 1981-2008, linked to their siblings and cousins. Cox regression was used to estimate associations between EDs and ADHD or ASD, and mediation analysis was used to assess the effects of intermediate mood or anxiety disorders. Polygenic scores (PGSs) were used to investigate the genetic association between anorexia nervosa (AN) and ADHD or ASD. Significantly increased risk for any ED was observed following an ADHD [hazard ratio = 1.97, 95% confidence interval = 1.75-2.22] or ASD diagnosis [2.82, 2.48-3.19]. Mediation analysis suggested that intermediate mood or anxiety disorders could account for 44-100% of the association between ADHD or ASD and ED. Individuals with a full sibling or maternal halfsibling with ASD had increased risk of AN [1.54, 1.33-1.78; 1.45, 1.08-1.94] compared to those with siblings without ASD. A positive association was found between ASD-PGS and AN risk [1.06, 1.02-1.09]. In this study, positive phenotypic associations between EDs and ADHD or ASD, mediation by mood or anxiety disorder, and a genetic association between ASD-PGS and AN were observed. These findings could guide future research in the development of new treatments that can mitigate the development of EDs among individuals with ADHD or ASD.

A comprehensive analysis of age of onset and cumulative incidence of mental disorders: A Danish register study

BACKGROUND

The age of onset (AOO), incidence and cumulative incidence of mental disorders are critical epidemiological measures, providing essential insights into the development and course of these disorders across the lifespan. This study aims to provide up-to-date estimates of the AOO, age-specific incidence, and cumulative incidence for a comprehensive range of mental disorders using data from Danish registers.

METHODS

We conducted a follow-up study encompassing all Danish residents from January 1, 2004, to December 31, 2021, totaling 91,613,465 person-years. Data were sourced from the Danish Psychiatric Central Research Register, identifying individuals treated for various mental disorders in psychiatric hospitals, outpatient departments, and accident/emergency departments, that is, treated in secondary care settings. We investigated specific categories of mental disorders, including substance abuse disorders, schizophrenia, mood disorders, anxiety, eating disorders, borderline personality disorders, intellectual disabilities, pervasive developmental disorders, and behavioral and emotional disorders. Age-sex-specific incidence rates were estimated using Poisson generalized linear models, and cumulative incidence was calculated using Aalen-Johansen's competing risks model. The study provides estimates of AOO, incidence, and cumulative incidence for various mental disorders, including their age and sex distributions.

RESULTS

The cumulative incidence by age 80 years for any mental disorder was 30.72% (95% confidence interval: 30.62%-30.83%) for males and 34.46% (34.35%-34.57%) for females. The most common types of mental disorders were anxiety-related disorders 16.27% (16.19%-16.36%) for males and 23.39% (23.29%-23.50%) for females, and followed by mood disorder 10.34% (10.27%-10.41%) for males and 16.67% (16.58%-16.77%) for females. For those who develop mental disorder, half will have developed their disorder by approximately age 22 years (median and interquartile range: males 21.37 (11.85-36.00); females 22.55 (16.31-36.08)).

CONCLUSIONS

Approximately one in three individuals will seek treatment for at least one mental disorder in a secondary care setting by age 80. Given that half of these individuals develop mental disorders before age 22, it is crucial to tailor service planning to meet the specific needs of young individuals. Web-based interactive data-visualization tools are provided for clinical utility.

Prevalence and Incidence Trends of Attention Deficit/Hyperactivity Disorder in Children and Youth Aged 1-24 Years in Ontario, Canada: A Validation Study of Health Administrative Data Algorithms: Tendances de la prévalence et de l'incidence du trouble de déficit de l'attention/hyperactivité chez les enfants et les jeunes âgés de 1 à 24 ans, en Ontario, Canada: une étude de validation des algorithmes de données administratives de santé

OBJECTIVE

To estimate prevalence and incidence rates over time in children and youth with attention deficit/hyperactivity disorder from the validation of population-based administrative data algorithms using family physicians' electronic medical records as a reference standard.

METHODS

A retrospective cohort study was conducted in Ontario, Canada to identify attention deficit/hyperactivity disorder among children and youth aged 1-24 years in health administrative data derived from case-finding algorithms using family physicians' electronic medical records. Multiple administrative data algorithms identifying attention deficit/hyperactivity disorder cases were developed and tested from physician-diagnosis of attention deficit/hyperactivity disorder in the electronic medical record to determine their diagnostic accuracy. We calculated algorithm performance using sensitivity, specificity, and predictive values. The most optimal algorithm was used to estimate prevalence and incidence rates of attention deficit/hyperactivity disorder from 2014 to 2021 in Ontario.

RESULTS

The optimal performing algorithm was "2 physician visits for attention deficit/hyperactivity disorder in 1 year or 1 attention deficit/hyperactivity disorder-specific prescription" with sensitivity: 83.2% (95% confidence interval [CI], 81.8% to 84.5%), specificity: 98.6% (95% CI, 98.5% to 98.7%), positive predictive value: 78.6% (95% CI, 77.1% to 80.0%) and negative predictive value: 98.9% (95% CI, 98.8% to 99.0%). From 2014, prevalence rates for attention deficit/hyperactivity disorder increased from 5.29 to 7.48 per 100 population in 2021 (N = 281,785). Males had higher prevalence rates (7.49 to 9.59 per 100 population, 1.3-fold increase) than females (2.96-5.26 per 100 population, 1.8-fold increase) from 2014 to 2021. Incidence rates increased from 2014 (0.53 per 100 population) until 2018, decreased in 2020 then rose steeply in 2021 (0.89 per 100 population, N = 34,013). Males also had higher incidence rates than females from 2014 to 2020 with females surpassing males in 2021 (0.70-0.81 per 100 male population,1.2-fold increase versus 0.36-0.97 per 100 female population, 2.7-fold increase).

CONCLUSIONS

Attention deficit/hyperactivity disorder is increasing in prevalence. We developed an administrative data algorithm that can reliably identify children and youth with attention deficit/hyperactivity disorder with good diagnostic accuracy.

Diagnosed eating disorders in Danish registers - incidence, prevalence, mortality, and polygenic risk

Eating disorders are a group of severe and potentially enduring psychiatric disorders associated with increased mortality. Compared to other severe mental illnesses, they have received relatively limited research attention. Epidemiological studies often only report relative measures despite these being difficult to interpret having limited practical use. The aims of this study were to evaluate the incidence and prevalence of diagnosed anorexia nervosa (AN), bulimia nervosa, and eating disorder not otherwise specified recorded in Danish hospital registers and estimate both relative and absolute measures of subsequent mortality - both all-cause and cause-specific in a general nationwide population of 1,667,374 individuals. In a smaller, genetically informed case-cohort sample, the prediction of polygenic scores for AN, body fat percentage, and body mass index on AN prevalence and severity was estimated. Despite males being less likely to be diagnosed with an eating disorder, those that do have significantly increased rates of mortality. AN prevalence was highest for individuals with high AN and low body fat percentage/body mass index polygenic scores.

Maternal asthma and asthma exacerbation during pregnancy and attention-deficit/hyperactivity disorder in offspring: a population-based cohort study

The link between inflammatory disorders, such as asthma, and attention deficit hyperactivity disorder (ADHD) is attracting increasing attention but few studies have examined cross-generational associations. We sought to examine associations of maternal asthma and asthma exacerbation during pregnancy, as well as paternal asthma, with the risk of ADHD in children. This population-based cohort study used data from the Taiwan National Health Insurance Research Database from 2004 to 2017. Cox regression models compared the risk of ADHD in children of parents with and without asthma, adjusting for parental sociodemographic, physical, and mental health conditions, as well as the child's birth weight, and number of births. A sibling control approach was employed to compensate for unmeasured confounders of asthma exacerbation during pregnancy. In the fully adjusted models, maternal and paternal asthma were both significantly associated with an increased risk of ADHD in offspring, with hazard ratios (HRs) of 1.36 (1.31-1.40) and 1.10 (1.05-1.14), respectively. Acute asthma exacerbation during pregnancy was not associated with the risk of further offspring ADHD (adjusted HR 1.00, 95% CI: 0.75-1.34). Both maternal and paternal asthma are associated with an increased risk of ADHD in offspring. The risk was higher from maternal asthma. However, no such association was found with maternal asthma exacerbation during pregnancy of sibling comparison.

Identifying non-adult attention-deficit/hyperactivity disorder individuals using a stacked machine learning algorithm using administrative data population registers in a universal healthcare system

Background

This research project aims to build a Machine Learning algorithm (ML) to predict first-time ADHD diagnosis, given that it is the most frequent mental disorder for the non-adult population.

Methods

We used a stacked model combining 4 ML approaches to predict the presence of ADHD. The dataset contains data from population health care administrative registers in Catalonia comprising 1,225,406 non-adult individuals for 2013-2017, linked to socioeconomic characteristics and dispensed drug consumption. We defined a measure of proper ADHD diagnoses based on medical factors.

Results

We obtained an AUC of 79.6% with the stacked model. Significant variables that explain the ADHD presence are the dispersion across patients' visits to healthcare providers; the number of visits, diagnoses related to other mental disorders and drug consumption; age, and sex.

Conclusions

ML techniques can help predict ADHD early diagnosis using administrative registers. We must continuously investigate the potential use of ADHD early detection strategies and intervention in the health system.

High-dose vitamin D3 supplementation in pregnancy and risk of neurodevelopmental disorders in the children at age 10: A randomized clinical trial

BACKGROUND

Vitamin D deficiency in pregnancy may increase the risk of autism and attention deficit hyperactivity disorder (ADHD).

OBJECTIVE

The objective of this study was to estimate the effect of vitamin D3 supplementation in pregnancy on risk of autism and ADHD.

DESIGN

This randomized clinical trial was part of the COpenhagen Prospective Study on Neuro-PSYCHiatric Development (COPYCH) project nested within the Copenhagen Prospective Studies on Asthma in Childhood 2010 (COPSAC2010) cohort comprising a population-based sample of 700 healthy mother-child pairs enrolled at week 24 of pregnancy. Maternal 25-hydroxy-vitamin D (25(OH)D) was measured at inclusion and 623 mothers were randomized 1:1 to either high-dose (2800 IU/d) or standard dose (400 IU/d) vitamin D3 until 1 wk postpartum (315 received high-dose, 308 standard dose). At age 10, diagnoses and symptom load of autism and ADHD, respectively, were established using the Kiddie-Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version.

RESULTS

The psychopathologic evaluation was completed by 591 children aged 10 y, and 16 children (2.7%) were diagnosed with autism and 65 (11.0%) with ADHD. Hereof, 496 children participated in the vitamin D3 trial (246 received high-dose, 250 standard dose). Of these, 12 children (2.4%) were diagnosed with autism and 58 (11.7%) with ADHD. Higher maternal preintervention 25(OH)D levels were associated with a decreased risk of autism [odd ratio (OR) per 10 nmol/L: 0.76 (0.59,0.97); P = 0.034], lower autistic symptom load [β per 10 nmol/L: -0.03 (-0.05,0.00); P = 0.024), and decreased risk of ADHD diagnosis (OR per 10 nmol/L: 0.88 (0.78,0.99); P = 0.033]. High-dose vitamin D3 supplementation was not associated with risk of autism or ADHD.

CONCLUSIONS

Higher maternal preintervention 25(OH)D was associated with a decreased risk of autism, lower autistic symptom load, and decreased risk of ADHD diagnosis, but high-dose vitamin D3 supplementation in pregnancy had no effect on risk of autism and ADHD. This trial was registered at clinicaltrials.gov as NCT00856947.

The correlates of neonatal complement component 3 and 4 protein concentrations with a focus on psychiatric and autoimmune disorders

Complement components have been linked to schizophrenia and autoimmune disorders. We examined the association between neonatal circulating C3 and C4 protein concentrations in 68,768 neonates and the risk of six mental disorders. We completed genome-wide association studies (GWASs) for C3 and C4 and applied the summary statistics in Mendelian randomization and phenome-wide association studies related to mental and autoimmune disorders. The GWASs for C3 and C4 protein concentrations identified 15 and 36 independent loci, respectively. We found no associations between neonatal C3 and C4 concentrations and mental disorders in the total sample (both sexes combined); however, post-hoc analyses found that a higher C3 concentration was associated with a reduced risk of schizophrenia in females. Mendelian randomization based on C4 summary statistics found an altered risk of five types of autoimmune disorders. Our study adds to our understanding of the associations between C3 and C4 concentrations and subsequent mental and autoimmune disorders.

Psychiatric disorders in paediatric-onset immune-mediated inflammatory diseases: a nationwide Danish study

OBJECTIVES

To investigate the frequency of psychiatric disorders before and after onset of paediatric-onset immune-mediated inflammatory diseases (pIMID).

STUDY DESIGN

In a nationwide study from 1996 to 2018, we investigated psychiatric disorders in patients with paediatric-onset inflammatory bowel diseases, autoimmune liver diseases and rheumatic diseases, using Danish national healthcare and population registers. Each case was matched with up to 10 controls from the background population. The cumulative incidence for psychiatric disorders prior to pIMID onset in patients was compared with controls. Cox proportional regression was used to estimate adjusted HRs (aHR) with a 95% CI between cases and controls after the index date.

RESULTS

We included 11 208 cases (57% female) and 98 387 controls. The median age at disease onset was 12.5 years (IQR 8-15) and follow-up time 9.8 years (IQR 5-15). We found an association between psychiatric disorders before index date and a diagnosis of subsequent pIMID (OR 1.3, 95% CI 1.2 to 1.4). Notably, after index date, cases also had an increased risk (aHR 1.6, 95% CI 1.5 to 1.7) of psychiatric disorders compared with controls. This risk was increased for all groups of psychiatric disorders. Female patients had an increased risk of suicide attempt after index date (aHR 1.4, 95% CI 1.1 to 1.8).

CONCLUSION

Patients with pIMID are at increased risk for a broad spectrum of psychiatric disorders both before and after onset of pIMID. The results support the need for awareness of psychiatric morbidity in this young patient group and the need for coordinated healthcare for those with comorbid states.

Prenatal Antidepressant Exposure and the Risk of Attention-Deficit/Hyperactivity Disorder in Childhood: Accounting for Misclassification of Exposure

BACKGROUND

Many studies of prenatal antidepressant exposure and the risk of attention-deficit/hyperactivity disorder (ADHD) have done little to reduce bias from exposure misclassification. We assessed the prenatal antidepressant-ADHD effect by incorporating information on repeatedly redeemed prescriptions and redemptions of drug classes commonly used in pregnancy in the analyses to reduce bias from exposure misclassification.

METHODS

Using population-based registries, we conducted a nationwide cohort study of all children born in Denmark from 1997 to 2017. In a former-user analysis, we compared children prenatally exposed, defined by a redeemed prescription by the mother during pregnancy, to a comparison cohort consisting of prenatally unexposed children whose mothers had redeemed a prescription before pregnancy. We incorporated information on repeatedly redeemed prescriptions and redemptions of drug classes commonly used in pregnancy in the analyses to reduce bias from exposure misclassification. We used incidence rate ratios (IRRs) and incidence rate differences (IRDs) as effect measures.

RESULTS

The cohort included 1,253,362 children, among whom 24,937 were prenatally exposed to antidepressants. The comparison cohort consisted of 25,698 children. During follow-up, 1,183 exposed children and 1,291 children in the comparison cohort developed ADHD yielding an IRR of 1.05 (95% confidence interval [CI] = 0.96, 1.15) and an IRD of 0.28 (95% CI = -0.20, 0.80) pr. 1,000 person-years. IRRs from analyses attempting to reduce exposure misclassification varied from 1.03 to 1.07.

CONCLUSIONS

Our results were not consistent with the hypothesized effect of prenatal antidepressant exposure on the risk of ADHD. Attempts to reduce exposure misclassification did not alter this finding.

Prenatal exposure to pregabalin, birth outcomes and neurodevelopment - a population-based cohort study in four Nordic countries

INTRODUCTION

Pregabalin is an antiepileptic drug frequently prescribed to pregnant women. Risks of adverse birth and postnatal neurodevelopmental outcomes following prenatal exposure to pregabalin are uncertain.

OBJECTIVE

To investigate the association between prenatal exposure to pregabalin and the risks of adverse birth and postnatal neurodevelopmental outcomes.

METHODS

This study was conducted using population-based registries in Denmark, Finland, Norway, and Sweden (2005-2016). We compared pregabalin exposure against no exposure to antiepileptics and against active comparators lamotrigine and duloxetine. We obtained pooled propensity score-adjusted estimates of association using fixed-effect and Mantel-Haenszel (MH) meta-analyses.

RESULTS

The total number of pregabalin-exposed births was 325/666,139 (0.05%) in Denmark, 965/643,088 (0.15%) in Finland, 307/657,451 (0.05%) in Norway, and 1275/1,152,002 (0.11%) in Sweden. The adjusted prevalence ratios (aPRs) with 95% confidence interval (CI) following pregabalin exposure versus no exposure were 1.14 (0.98-1.34) for major congenital malformations and 1.72 (1.02-2.91) for stillbirth, which attenuated to 1.25 (0.74-2.11) in MH meta-analysis. For the remaining birth outcomes, the aPRs were close to or attenuated toward unity in analyses using active comparators. Adjusted hazard ratios (95% CI) contrasting prenatal pregabalin exposure versus no exposure were 1.29 (1.03-1.63) for ADHD and attenuated when using active comparators, 0.98 (0.67-1.42) for autism spectrum disorders, and 1.00 (0.78-1.29) for intellectual disability.

CONCLUSIONS

Prenatal exposure to pregabalin was not associated with low birth weight, preterm birth, small for gestational age, low Apgar score, microcephaly, autism spectrum disorders, or intellectual disability. On the basis of the upper value of the 95% confidence interval, increased risks greater than 1.8 were unlikely for any major congenital malformation and ADHD. For stillbirth and most groups of specific major congenital malformations, the estimates attenuated in MH meta-analysis.

School performance and psychiatric comorbidity in childhood absence epilepsy: A Danish cohort study

The aim was to determine school performance and psychiatric comorbidity in children with childhood absence epilepsy (CAE). We reviewed the medical records in children with ICD-10 codes for idiopathic generalized epilepsy before 18 years of age, and pediatric neurologists confirmed the International League Against Epilepsy criteria for CAE were met. Control groups were the general pediatric population or children with non-neurological chronic disease. Outcomes were from nationwide and population-based registers on school performance and psychiatric comorbidity. We compared the mean grade point average using linear regression and estimated hazard ratios (HR) using Cox regression for the other outcomes. Analyses were adjusted for the child's sex, and year of birth, and parental highest education, receipt of cash benefits or early disability pension. We included 114 children with CAE with a median age at onset of 5.9 years (interquartile range = 4.5-7.3 years). Compared with both population controls and non-neurological chronically ill children, children with CAE had increased hazard of special needs education (HR = 2.7, 95% confidence interval (CI) = 1.8-4.1, p < 0.0001), lower grade point average at 9th grade by 1.7 grade points (95% CI = -2.5 to -1.0, p < 0.001), increased ADHD medicine use (HR = 4.4, 95% CI = 2.7-7.2, p < 0.001), increased sleep medicine use (HR = 2.7, 95% CI = 1.7-4.3, p < 0.001), and increased psychiatry visits (HR = 2.1, 95% CI = 1.1-4.0, p = 0.03). In conclusion, children with CAE have increased psychiatric comorbidity and a considerable proportion of these children receive special needs education in primary/secondary school, albeit insufficient to normalize their considerably lower grade point average in the 9th grade.

Long-Term Morbidity and Mortality in Children After In Utero Exposure to Maternal Cancer

PURPOSE

In utero exposure to maternal cancer and cancer treatment might influence the child's short- and long-term health and development. The objective of the study was to investigate short- and long-term somatic and psychiatric outcomes in children exposed to maternal cancer in utero.

METHODS

This nationwide cohort study identified all liveborn children in Denmark between January 1978 and December 2018. Exposure was defined as maternal cancer diagnosis during pregnancy, and in a subgroup analysis, exposure to chemotherapy in utero. The main outcomes of interest were overall mortality, somatic diagnoses, and psychiatric diagnoses identified in the National Health Registers. Follow-up started at birth and ended at an event, death, emigration, or end of 2018. Hazard ratios of end points adjusted for potential confounders were estimated using Cox regression analysis.

RESULTS

Of 2,526,163 included liveborn children, 690 (0.03%) were exposed to maternal cancer in utero. Compared with unexposed fetuses, children exposed in utero had no higher overall mortality, adjusted hazard ratio 0.8 (95% CI, 0.4 to 1.5), nor increased risk of congenital malformations, overall somatic or psychiatric disease. During the period 2002-2018, of 378 (0.03%) children exposed to cancer in utero, 42 (12.5%) were exposed to chemotherapy. Among these 42 children, in utero exposure to chemotherapy was not associated with selected somatic diseases nor to congenital malformations when compared with in utero exposure to maternal cancer without chemotherapy.

CONCLUSION

Overall, findings did not indicate excess risk of mortality or severe morbidity among children exposed to cancer in utero. Fetal exposure to chemotherapy was not associated with adverse health outcomes in childhood.

Association of Prenatal Exposure to Benzodiazepines and Z-Hypnotics With Risk of Attention-Deficit/Hyperactivity Disorder in Childhood

IMPORTANCE

Evidence is limited regarding the safety of prenatal benzodiazepine and z-hypnotic exposure and its association with long-term neurodevelopment in childhood.

OBJECTIVE

To quantify the associations of the timing and number of intervals of prenatal exposure to benzodiazepines and/or z-hypnotics with the risk of attention-deficit/hyperactivity disorder (ADHD) in childhood.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study used data from the 1999 to 2008 population-based Norwegian Mother, Father and Child Cohort Study, which are linked to the Medical Birth Registry of Norway, Norwegian Patient Registry, and Norwegian Prescription Database. Two populations of participants were created: a full sample and a mental health sample. The full sample included mothers and their live-born singletons, whereas the mental health sample was restricted to offspring of mothers who reported anxiety, depression, or sleeping problems during pregnancy or 6 months before pregnancy. Data were analyzed from September 2021 to February 2022.

EXPOSURES

Maternal self-report of benzodiazepine and/or z-hypnotic use during pregnancy was grouped into early pregnancy exposure and middle and/or late pregnancy exposure for analysis of the association with timing of exposure, and number of 4-week intervals of exposure was classified (single [1] vs multiple [≥2]) for analysis of the association with number of exposed intervals.

MAIN OUTCOME AND MEASURES

The outcome was ADHD, defined as time to ADHD diagnosis or filled prescription for ADHD medication. To control for confounding, inverse probability of treatment-weighted Cox proportional hazards regression models were used. Hazard ratios and 95% CIs were estimated. The weights were derived from propensity score modeling of the probability of benzodiazepine and/or z-hypnotic exposure as a function of potential confounders between the exposure and the outcome, including maternal symptoms of depression and anxiety.

RESULTS

The full sample comprised 82 201 pregnancies, and the mental health sample included 19 585 pregnancies. In total, 681 offspring (0.8%) in the full sample and 468 offspring (2.4%) in the mental health sample were prenatally exposed to benzodiazepines and/or z-hypnotics. After weighting, exposure in early (hazard ratio, 0.74; 95% CI, 0.39-1.94) and middle and/or late (hazard ratio, 0.76; 95% CI, 0.35-1.61) pregnancy was not associated with increased risk of childhood ADHD. There was no evidence of substantial association between the number of exposed intervals during pregnancy and childhood ADHD.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that there may be no increased risk of childhood ADHD associated with prenatal exposure to benzodiazepines and/or z-hypnotics, regardless of timing of exposure and number of exposed intervals. However, these findings should be interpreted with caution due to low study power.

Associations between parental socioeconomic-, family-, and sibling status and risk of eating disorders in offspring in a Danish national female cohort

OBJECTIVE

Studies on parental socioeconomic status (SES) and family risk factors for eating disorders (EDs) have yielded inconsistent results; however, several studies have identified high parental educational attainment as a risk factor. The aim was to evaluate associations of parental SES and family composition with anorexia nervosa (AN), bulimia nervosa (BN), and eating disorders not otherwise specified (EDNOS) in the offspring, adjusting for parental age and parental mental health.

METHODS

The cohort included women born in Denmark between January 1, 1989 and December 31, 2010, derived from Danish national registers. Each person was followed from their sixth birthday until onset of the disorder of interest or to December 31, 2016. Exposure variables were: childhood SES, defined as individually evaluated parental level of income, occupation, and education; sibling status; and family composition. Outcomes were: AN, BN, EDNOS, and major depressive disorder (MDD), included as a psychiatric comparison disorder. Risks were estimated using Cox proportional hazards.

RESULTS

High parental SES was associated with increased risk of especially AN, and less so BN and EDNOS, in offspring. In comparison, low SES was associated with a higher risk of MDD. No differences between maternal or paternal socioeconomic risk factors were found. Family composition and sibling status showed limited influence on ED risk.

DISCUSSION

SES shows opposite associations with AN than MDD, whereas associations with BN and EDNOS are intermediate. The socioeconomic backdrop of AN differs markedly from that reported in other psychiatric disorders. Whether that is due to genetic and/or environmental factors remains unknown.

PUBLIC SIGNIFICANCE STATEMENT

Parental socioeconomic background (SES) may influence eating disorders risk in offspring somewhat differently than other psychiatric disorders. In Denmark, higher parental SES was associated with increased risk of, particularly, anorexia nervosa (AN). Importantly AN does strike across the SES spectrum. We must ensure that individuals of all backgrounds have equal access to care and are equally likely to be detected and treated appropriately for eating disorders.

Motor development problems in infancy predict mental disorders in childhood: a longitudinal cohort study

The purpose of this study is to examine whether motor development problems in infancy predicted mental disorders later in childhood, taking a wide array of potential confounding variables into consideration. This longitudinal study included an unselected study population of 33238 newborn children from the Copenhagen area, Denmark. Data on the predictor variable, motor development problems at 8-10 months of age, were obtained from the community health nurses' systematic evaluation of the child's motor development during a home visit and stored in the Child Health Database. Data on outcome, diagnosed mental disorders before the age of 8 years, were obtained from the Danish National Patient Register. Potential confounding variables were obtained from the Child Health Database, the National Birth Register and the Civil Registration System. The prevalence of motor development problems at 8-10 months of age was 19.3%; the incidence of any diagnosed mental disorder from 11 months of age to the 8th birthday was 4.0%. Motor development problems were associated with an increased risk of being diagnosed with a mental disorder before the 8th birthday, adjusted odds ratio (AOR) 1.47 (1.29-1.67). Motor development problems were associated with later neurodevelopmental disorders, AOR 1.77 (1.52-2.06), in particular autism spectrum disorders, AOR 1.63 (1.31-2.03), hyperactivity/attention deficit disorders, AOR 1.29 (1.03-1.61) and disorders of intellectual disability, AOR 3.28 (2.39-4.49).

CONCLUSION

Motor development problems as early at 8-10 months of age were predictive of neurodevelopmental disorders before the 8th birthday. The findings call for clinical attention and more research on preventive potentials in the community child health care.

WHAT IS KNOWN

• Children with ASD, ADHD and ID have high prevalence of early motor development problems.

WHAT IS NEW

• Motor development problems in infancy predicted neurodevelopmental disorders before the 8th birthday. • This observation could improve early identification and prevention of mental health problems in childhood.

Increased risk of somatic diseases following anorexia nervosa in a controlled nationwide cohort study

OBJECTIVE

To assess the risk of somatic diseases in connection with anorexia nervosa (AN).

METHOD

This matched cohort study was based on Danish registries of all patients born 1961-2008 with a first-time diagnosis of AN in 1994-2018 at age 8-32 and matched controls without an eating disorder. For 13 somatic disease categories, time from inclusion date to time of first somatic diagnosis, accounting for censoring, was studied by use of time-stratified Cox models.

RESULTS

A total of 9985 AN patients born 1961-2008 and 49,351 controls were followed for a median (interquartile range) of 9.0 (4.4-15.7) years. During the first 2 years after entry there was a 60% higher hazard for any somatic disease among patients with AN than among controls, while the ratio from three to 11 years was reduced to 1.18. Regardless of age at diagnosis, the hazard among patients and controls were no different at approximately a decade after diagnosis of AN and the cumulative risk for patients for 12 of 13 disease categories was always higher or no less that for controls. For all disease categories, the hazard ratio (HR) was higher when close to entry. For most disease categories, age at diagnosis of AN did not modify the effect.

DISCUSSION

While around 90% of all individuals had any somatic disease at the end of follow-up, the cumulative incidence over time was higher for patients with AN than for controls. Large HRs were seen in the early years after diagnosis during which patients require extensive medical interventions.

PUBLIC SIGNIFICANCE

Based on Danish registries, a large sample of almost 10,000 patients with AN born 1961-2008 and almost 50,000 matched controls were followed for a median of 9 years. While around 90% of all individuals had any somatic disease at the end of follow-up, the cumulative incidence over time was higher for patients with AN than for controls.

Association of Maternal Use of Triptans During Pregnancy With Risk of Attention-Deficit/Hyperactivity Disorder in Offspring

Importance

Triptans are commonly used in the treatment of migraine. Prenatal exposure to triptans may be associated with adverse fetal neurodevelopment; however, there is limited information about the long-term safety of triptan use during pregnancy.

Objective

To examine the association between maternal use of triptans during pregnancy and diagnosis and symptoms of attention-deficit/hyperactivity disorder (ADHD) among offspring.

Design, Setting, and Participants

This study used data from the Norwegian Mother, Father and Child Cohort Study (recruitment 1999-2008), linked to national health registries. Live-born singleton children born to women with migraine before or during pregnancy were included. Two analytic samples were defined: one to assess ADHD diagnosis and one to assess ADHD symptoms. Data were analyzed from May 1 to November 30, 2021.

Exposure

Maternal self-report of triptan use during pregnancy. Exposed children were compared with 2 groups of unexposed children whose mothers reported migraine (1) during pregnancy and (2) before pregnancy only.

Main Outcomes and Measures

An ADHD diagnosis was defined as diagnosis of hyperkinetic disorder or receipt of dispensed ADHD medication. Symptoms of ADHD at 5 years were measured by the Conners' Parent Rating Scale, where a higher score indicates more symptoms of ADHD. Cox proportional hazards regression models and generalized linear models with inverse probability weights were used to estimate weighted hazard ratios (HRs) and standardized mean differences, respectively, with 95% CIs.

Results

The ADHD diagnosis sample comprised 10 167 children (mean [SD] maternal age, 30.2 [4.6] years; 5231 boys [51.5%]), and the ADHD symptoms sample comprised 4367 children (mean [SD] maternal age, 30.6 [4.4] years; 2191 boys [50.2%]). Children were followed up for a mean (SD) of 10.6 (2.2) years. Children with prenatal triptan exposure had no increased risk of ADHD diagnosis compared with unexposed children whose mothers had migraine during pregnancy (weighted HR, 1.16; 95% CI, 0.78-1.74) and compared with unexposed children whose mothers had migraine only before pregnancy (weighted HR, 1.28; 95% CI, 0.84-1.94). There were no differences in ADHD symptom scores between exposed and unexposed children.

Conclusions and Relevance

The findings of this study suggest that there is no increased risk of ADHD among offspring associated with prenatal exposure to triptans.

School performance and psychiatric comorbidity in juvenile absence epilepsy and juvenile myoclonic epilepsy: a Danish population-based cohort study

BACKGROUND

We aimed to determine school performance and psychiatric comorbidity in juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), and generalized tonic-clonic seizures (GTCS) alone.

METHODS

All children (< 18 years) fulfilled International League Against Epilepsy criteria after review of their medical records. Control groups were the pediatric background population or children with non-neurological chronic disease. Outcomes were on school performance and psychiatric comorbidity. We compared mean grade point averages using linear regression and estimated hazard ratios using Cox regression in the remaining analyses. We adjusted for the child's sex, age, and year of birth; and parental highest education, receipt of cash benefits or early retirement.

RESULTS

We included 92 JAE, 190 JME, 27 GTCS alone, 15,084 non-neurological chronic disease controls, and population controls. JAE had two times increased hazard for special needs education compared with age-matched population controls (hazard ratio 2.2, 95% CI = 1.1‒4.6, p = 0.03); this was not seen in JME. Compared with population controls, both JAE and JME had lower grade point average in secondary and high school (JME: 9th grade:  - 0.5 points, 95% CI = -0.9 to -0.06, p = 0.03; high school:  - 0.6 points, 95% CI = -1.3 to -0.1, p = 0.04), and 8% fewer JME and 15% fewer JAE attended high school. Both JME and JAE had higher hazard for redeeming sleep medication compared with non-neurological chronic disease; additionally, JAE had increased hazard for ADHD medicine redemptions.

CONCLUSIONS

Both JAE and JME had marginally poorer school performance; performance seemed worse in JAE than in JME. Both JAE and JME had increased use of sleep medication.

Pre-eclampsia is associated with increased neurodevelopmental disorders in children with congenital heart disease

AIMS

Our primary aim was to examine whether exposure to pre-eclampsia increases the risk of neurodevelopmental disorders in children born with congenital heart disease (CHD). Our secondary aim was to evaluate whether CHD and pre-eclampsia may act in synergy and potentiate this risk.

METHOD AND RESULTS

Using population-based registries, we included all Danish children born with CHD between 1994 and 2017. Non-singletons and children born with a syndrome were excluded. Neurodevelopmental disorders including attention-deficit/hyperactivity disorder, autism spectrum disorders, and tic disorders were identified with the use of the 10th edition of International Classification of Disease (ICD-10) codes DF80-DF98. Using Cox proportional hazard regression, we estimated the risk of neurodevelopmental disorders in children with CHD exposed to pre-eclampsia compared with those with CHD not exposed to pre-eclampsia. The population consisted of 11 449 children born with CHD. Children exposed to pre-eclampsia had an increased risk of neurodevelopmental disorders, hazard ratio: 1.84 (95% confidence interval: 1.39-2.42). Furthermore, a comparison cohort of 113 713 children with no CHD diagnoses were included. Using cumulative incidence analyses with death as competing risk, we compared the risk of neurodevelopmental disorders if exposed to pre-eclampsia among children with CHD and children without CHD. Exposure to pre-eclampsia drastically increased the cumulative incidence of neurodevelopmental disorders in children born with CHD.

CONCLUSION

Exposure to pre-eclampsia is associated with increased risk of neurodevelopmental disorders in children born with CHD. CHD and pre-eclampsia may act in synergy and potentiate this effect. Clinicians should therefore be especially attentive to neurodevelopmental problems in this vulnerable subgroup.

Prenatal antidepressant exposure and the risk of attention-deficit/hyperactivity disorder in childhood: A cohort study with triangulation

BACKGROUND

Uncontrolled confounding from maternal depression and genetic and environmental factors is expected in studies investigating the effect of prenatal antidepressant exposure on the risk of attention-deficit/hyperactivity disorder (ADHD) in childhood and may explain inconsistencies in the existing evidence. We aimed to assess this effect using triangulation.

METHODS

Using population-based health registries, we conducted a nationwide cohort study of all children born in Denmark between 1997 and 2017 and followed through 2018 for ADHD. We assessed the effect of prenatal antidepressant exposure on the risk of ADHD in childhood by comparing children with and without prenatal antidepressant exposure in terms of adjusted incidence rate ratios (IRRs), adjusted incidence rate differences (IRDs), and adjusted risk differences (RDs) and the associated 95% confidence intervals (CIs). We triangulated results from four different analytic approaches: an overall analysis, a negative control analysis, a sibling analysis and a former-user analysis.

RESULTS

The overall study cohort consisted of 1,253,362 children, among whom 28,910 (2.3%) had prenatal antidepressant exposure. ADHD during follow-up was diagnosed among 1,411 (4.9%) of the exposed and in 37,196 (3.0%) of the unexposed children. Triangulation suggested an IRR of 1.09-1.15; an IRD less than 1 case/1,000 person-years, and an RD of 0.9%-2.2% over an up to 18-year period.

CONCLUSIONS

Based on triangulation, we estimated a modest effect of prenatal antidepressant exposure on the risk of ADHD in childhood. However, considering the limitations of our approaches, this observed association may be partially due to residual biases.

Medical disorders in a Danish cohort of children with attention-deficit hyperactivity disorder

Studies have identified a higher prevalence of co-existing psychiatric and medical disorders in children with ADHD. There is a shortage of longitudinal studies providing an overview of potential medical disorders in children with ADHD. The objective of this study was to provide a broad overview of lifetime prevalence and relative risk of medical disorders in a nationwide Danish cohort of children with and without ADHD during the first 12 years of life. A population-based prospective follow-back cohort study used data from Danish national health registries to identify a cohort of all children born in Denmark between 1995 and 2002. The children were followed from birth until 12 years of age in two national registries. Children with ADHD had a significantly higher prevalence of recorded diagnoses across all included chapters of medical disorders in the ICD-10, except for neoplasms, where the association with ADHD was non-significant. The highest relative risk was observed for the chapter concerning diseases of the nervous system, with episodic and paroxysmal disorders being the most frequently registered underlying category. The findings indicate that children with ADHD have an increased risk of a broad range of medical disorders compared to the general population during the first 12 years of life, except for neoplasms.

Infancy weight faltering and childhood neurodevelopmental disorders: a general population birth-cohort study

While it is known that intrauterine growth restriction is associated with later mental disorders, it is still unclear whether similar associations exists for postnatal weight faltering, also known as 'failure to thrive' in infancy. This study examined the potential connection between infancy weight faltering and mental disorders diagnosed in childhood focusing specifically on neurodevelopmental disorders. The Copenhagen Child Cohort (CCC2000) was used to explore weight gain in infancy assessed by community health nurses. Data from the Danish national registries were used to quantify ICD-10 mental disorders diagnosed between birth and 12 years of age, as well as potential child and family confounders. Of 4.476 children with sufficient weight data, 339 (7.3%) children were diagnosed with a mental disorder in childhood. Both any (weight gain < -1SD) and severe infancy weight faltering (weight gain < -2SD) were associated with psychomotor delays, while severe infancy weight faltering was also associated with intellectual impairments. Notably, no significant associations were found between weight faltering and autism spectrum disorders or attention deficit hyperactivity disorders. Weight faltering in infancy may be an early marker of neurodevelopmental delays. This possibility should be considered when assessing infants with slow weight gain, to early identification and treatment of co-occurring neurodevelopmental disorders.

Association of labour epidural analgesia with neurodevelopmental disorders in offspring: a Danish population-based cohort study

BACKGROUND

Whether labour epidural analgesia impacts risk of neurodevelopmental disorders in offspring is unsettled, raising public and scientific concerns. We explored the association between maternal labour epidural analgesia and autism spectrum disorder, and specific developmental disorder, attention-deficit hyperactivity disorder, intellectual disability, and epilepsy in offspring.

METHODS

This nationwide population-based cohort study included 624 952 live-born singletons delivered by women who intended to deliver vaginally (i.e. vaginal and intrapartum Caesarean deliveries) in Denmark from 2005 to 2016. A total of 80 862 siblings discordant for exposure to labour epidural analgesia were analysed in a sibling-matched analysis. Both full-cohort and sibling-matched analyses were performed to estimate hazard ratios (HRs) of offspring risk of autism spectrum disorder, specific developmental disorder, attention-deficit hyperactivity disorder, intellectual disability, and epilepsy, according to exposure to labour epidural analgesia, adjusted for maternal socio-economic, pregnancy, and perinatal covariates.

RESULTS

In the full cohort, maternal labour epidural analgesia was associated with autism spectrum disorder in offspring (HR 1.11; 95% confidence interval [CI]: 1.04-1.18); however, in the sibling-matched analysis, no association with autism spectrum disorder was found (HR 1.03; 95% CI: 0.84-1.27). The association between labour epidural analgesia and specific developmental disorder (HR 1.12; 95% CI: 1.03-1.22) in the full cohort also disappeared in the sibling-matched analysis (HR 1.01; 95% CI: 0.78-1.31). No association between maternal labour epidural analgesia and the remaining neurodevelopmental disorders was found overall (attention-deficit hyperactivity disorder, HR 0.98; 95% CI: 0.92-1.03; intellectual disability, HR 0.98; 95% CI: 0.85-1.14; epilepsy, HR 0.89; 95% CI: 0.79-1.00) or in the sibling-matched analyses.

CONCLUSIONS

Our findings did not support an association between maternal attention-deficit hyperactivity disorder and autism spectrum disorder, specific developmental disorder, attention-deficit hyperactivity disorder, intellectual disability, or epilepsy.

Trace elements in drinking water and the incidence of attention-deficit hyperactivity disorder

BACKGROUND

Trace elements have been suggested to have neurotoxic effects and increase the risk of neurodevelopmental disorders, but studies of a potential role of trace elements in relation to Attention-Deficit/Hyperactivity Disorder (ADHD) are very limited. The objective of this study was to conduct an exploratory analysis investigating the associations between 17 geogenic trace elements (Ba, Co, Eu, I, Li, Mo, Rb, Re, Rh, Sb, Sc, Se, Si, Sr, Ti, U and Y) found in Danish drinking water and the risk of developing ADHD.

METHODS

In this cohort study, 284,309 individuals, born 1994-2007, were followed for incidence of ADHD from the age of five until the end of study, December 31, 2016. We conducted survival analyses, using Poisson regression to estimate incidence rate ratios (IRRs) with 95 % confidence intervals (CI) in three different confounder adjustment scenarios.

RESULTS

In a model including adjustments for age, sex, calendar year, parental socio-economic status, neighborhood level socio-economic status and parental psychiatric illness, we found that six of the 17 trace elements (Sr, Rb, Rh, Ti, Sb and Re) were associated with an increased risk of ADHD, whereas two (Ba and I) were inversely associated with ADHD. However, when including region as a covariate in the model, most trace elements were no longer associated with ADHD or the association changed direction. Four trace elements (I, Li, Rb, and Y) remained significantly associated with ADHD but in an inverse direction and for three of these (I, Li and Y), we found significant interactions with region in their association with ADHD.

CONCLUSION

The trace elements under investigation, at levels found in Danish drinking water, do not seem to contribute to the development of ADHD and our findings highlight the importance of examining consistency of associations across geographic areas.

Associations between patterns in comorbid diagnostic trajectories of individuals with schizophrenia and etiological factors

Schizophrenia is a heterogeneous disorder, exhibiting variability in presentation and outcomes that complicate treatment and recovery. To explore this heterogeneity, we leverage the comprehensive Danish health registries to conduct a prospective, longitudinal study from birth of 5432 individuals who would ultimately be diagnosed with schizophrenia, building individual trajectories that represent sequences of comorbid diagnoses, and describing patterns in the individual-level variability. We show that psychiatric comorbidity is prevalent among individuals with schizophrenia (82%) and multi-morbidity occur more frequently in specific, time-ordered pairs. Three latent factors capture 79% of variation in longitudinal comorbidity and broadly relate to the number of co-occurring diagnoses, the presence of child versus adult comorbidities and substance abuse. Clustering of the factor scores revealed five stable clusters of individuals, associated with specific risk factors and outcomes. The presentation and course of schizophrenia may be associated with heterogeneity in etiological factors including family history of mental disorders.

Incidence and comorbidities of disruptive behavior disorders diagnosed in Finnish specialist psychiatric services

PURPOSE

Disruptive behavior disorders (DBD), including oppositional defiant disorder (ODD) and conduct disorder (CD), are some of the most common psychiatric conditions in childhood. Despite this, there has been limited research on DBDs. We examined the incidence, comorbidity and gender differences of DBDs diagnosed by specialist services.

METHOD

This was a nationwide register study of 570,815 children and adolescents born in 1996-2005. The 7050 individuals diagnosed with DBD by specialist healthcare services were matched to 26,804 controls.

RESULTS

By the age of 15, the cumulative incidence of diagnosed DBDs was 3.5% for boys and 1.4% for girls. The yearly incidence rate increased for girls after 13 years of age, while the incidence for boys was relatively stable between 8 and 15 years of age. When we compared subjects born between 1996-1998 and 1999-2001, we found that by the age of 12, the cumulative incidence per 100 people had increased from 0.56 to 0.68 among girls and from 2.3 to 2.6 among boys. This indicated a minor increase in treated incidence. The parents of children diagnosed with DBDs had lower educational levels than the parents of controls. Children with DBD were also more likely to have been diagnosed with other psychiatric disorders.

CONCLUSION

Although DBDs were 3.5 times more common among boys during the whole follow-up period, the yearly incidence during adolescence was fairly similar between boys and girls. DBD existed alongside various psychiatric disorders at a relatively young age and only a minor increase in treated incidence was found during childhood.

Autism comorbidities show elevated female-to-male odds ratios and are associated with the age of first autism diagnosis

OBJECTIVE

To investigate the association between the comorbidity rates in autism and sex, birth year and the age at which autism was first diagnosed and compare the relative impact of each.

METHOD

Using the Danish National Patient Registry, cumulative incidences up to the age of 16 for 11 comorbid conditions (psychosis, affective disorders, anxiety disorders, conduct disorder, eating disorders, obsessive-compulsive disorder, attention-deficit hyperactivity disorder, epilepsy, tic disorders, sleep disorders or intellectual disability) were calculated for individuals with autism (N = 16,126) and non-autism individuals (N = 654,977). Individuals were further stratified based on the age at the first autism diagnoses and comorbid diagnoses up to the age of 16 were compared.

RESULTS

Most comorbidities were significantly associated with birth year and sex. Female/male odds ratios for 8 of 11 comorbid conditions were up to 67% higher than the corresponding odds ratios in the non-autism population, including conditions that are generally more common in males than in females as well as conditions that are more common in females. All comorbidity rates were significantly associated with the age at the first autism diagnosis, which was a stronger predictor than sex and birth year for 8 conditions.

CONCLUSIONS

Comorbidity rates for females exceed what would be expected based on the sex ratios among non-autistic individuals, indicating that the association between autism and comorbidity is stronger in females. Comorbidity rates are also highly dependent on the age at the first autism diagnosis, which may contribute to autism heterogeneity in research and clinical practice.

Genetic, Clinical, and Sociodemographic Factors Associated With Stimulant Treatment Outcomes in ADHD

OBJECTIVE

Stimulant medications are effective for treating attention deficit hyperactivity disorder (ADHD), yet discontinuation and switch to nonstimulant ADHD medications are common. This study aimed to identify genetic, clinical, and sociodemographic factors influencing stimulant treatment initiation, discontinuation, and switch to nonstimulants in individuals with ADHD.

METHODS

The authors obtained genetic and national register data for 9,133 individuals with ADHD from the Danish iPSYCH2012 sample and defined stimulant treatment initiation, discontinuation, and switch from prescriptions. For each stimulant treatment outcome, they examined associations with polygenic risk scores (PRSs) for psychiatric disorders and clinical and sociodemographic factors using survival analyses, and conducted genome-wide association studies (GWASs) and estimated single-nucleotide polymorphism heritability (h2SNP).

RESULTS

Eighty-one percent of the sample initiated stimulant treatment. Within 2 years, 45% discontinued stimulants and 15% switched to nonstimulants. Bipolar disorder PRS (hazard ratio=1.05, 95% CI=1.02, 1.09) and schizophrenia PRS (hazard ratio=1.07, 95% CI=1.03, 1.11) were associated with discontinuation. Depression, bipolar disorder, and schizophrenia PRSs were marginally but not significantly associated with switch (hazard ratio range, 1.05-1.07). No associations were observed for ADHD and autism PRSs. Individuals diagnosed with ADHD at age 13 or older had higher rates of stimulant initiation, discontinuation, and switch (hazard ratio range, 1.27-2.01). Psychiatric comorbidities generally reduced rates of initiation (hazard ratio range, 0.84-0.88) and increased rates of discontinuation (hazard ratio range, 1.19-1.45) and switch (hazard ratio range, 1.40-2.08). h2SNP estimates were not significantly different from zero. No GWAS hits were identified for stimulant initiation or discontinuation. A locus on chromosome 16q23.3 reached genome-wide significance for switch.

CONCLUSIONS

The study findings suggest that individuals with ADHD with higher polygenic liability for mood and/or psychotic disorders, delayed ADHD diagnosis, and psychiatric comorbidities have a higher risk for stimulant treatment discontinuation and switch to nonstimulants. Despite the study's limited sample size, one putative GWAS hit for switch was identified, illustrating the potential of utilizing genomics linked to prescription databases to advance ADHD pharmacogenomics.

Comorbid mental disorders during long-term course in a nationwide cohort of patients with anorexia nervosa

OBJECTIVE

Comorbid mental disorders in anorexia nervosa during long-term course require detailed studies.

METHOD

This matched cohort study was based on nationwide Danish register data of all patients born 1961-2008 with a first-time ICD-10 diagnosis of anorexia nervosa (AN) between 1994 and 2018 at age 8-32 and matched controls taken from all individuals without an eating disorder (ED). For nine categories of non-eating mental disorders, time from date of first AN-diagnosis (inclusion date) to time of first diagnosis, accounting for censoring, was studied by use of time-stratified Cox models.

RESULTS

A total of 9,985 patients with AN (93.5% females) and 49,351 matched controls were followed for a median (IQR) of 9.0 (4.4-15.7) years. For patients, there was about 25% and 55% risk of receiving any non-ED disorder during the first 2 years and two decades after inclusion, respectively. A hazard ratio (HR) of seven for any non-ED was found for the first 12 months after inclusion, a ratio that reduced to two at five or more years after inclusion. During the first years, large HRs ranging in 6-9 were found for affective, autism spectrum, personality, and obsessive-compulsive disorders with the latter displaying the highest continuous increased risk. The HR at 12 months after inclusion was highest for any non-ED disorder and affective disorders in patients aged 8-13 at diagnosis.

DISCUSSION

Comorbid mental disorders in AN are most frequently diagnosed in the first years after diagnosis of AN and on longer terms imply a double immediate risk.

Parental education, parent-child relations and diagnosed mental disorders in childhood: prospective child cohort study

BACKGROUND

Mental disorder in childhood is an important public health issue. We aimed to examine the prospective association between parental education at childbirth and diagnosed mental disorders in young children and explore whether this association was mediated or modified by parent-child relations in infancy.

METHODS

Prospective cohort study of all newborn was from 2002 to 2010 from 16 municipalities in the capital region of Copenhagen, Denmark, with follow-up until their 8th birthday, N = 40 762. Baseline data included information from national population registers and from health visitors' records at child aged 0 to 10 months. Outcome variable: any mental disorder diagnosed at hospital from age 11 months to 8 years.

RESULTS

Low parental education was predictive of diagnosed child mental disorder, adjusted odds ratio (AOR) = 1.83 (95% CI 1.49-2.23). Problematic parent-child relation at age 8-10 months was also predictive of mental disorder, AOR = 2.06 (1.57-2.70) but did not mediate the association between parental education and mental disorder. AOR for mental disorders was 3.24 (2.03-5.16 for the combination vocational training and problematic parent-child relation and 2.49 (1.42-4.38) for the combination primary school and problematic parent-child relation.

CONCLUSIONS

Low parental education and problematic parent-child relation were independent risk factors for diagnosed mental disorders in the age span of 11 months to 8 years.

Mental disorders in referred 0-3-year-old children: a population-based study of incidence, comorbidity and perinatal risk factors

The epidemiology of mental disorders in early childhood is still under-researched. We aim to explore the incidence, comorbidities and risk factors of mental disorders in 0-3-year-olds referred to hospital settings. In a national cohort of 918,280 children born in 1997-2010, we calculated incidence rates per 1,000 person-years (IR) of first-time mental and developmental disorders diagnosed in hospitals before four years of age. Data were obtained from Danish population registries. We used logistic regression to analyse co-morbidity and Cox proportional hazard models to evaluate the influence of pre- and perinatal risk factors. A total of 16,164 children (1.76%) were diagnosed with a mental (0.90%) or developmental disorder (1.05%). Pervasive developmental disorders (PDD) and disorders of hyperactivity and inattention (ADHD) were increasingly diagnosed with age. Feeding and eating disorders and disorders of social functioning were most frequent among the youngest children. Comorbidity was found in 18%, e.g., between PDD and ADHD (OR 135.8; 95% CI 112.0-164.7) or between ADHD and disorders of social functioning (OR 148.0; 95% CI 106.4-205.7). Young maternal age, old paternal age, maternal smoking in pregnancy, boy sex, premature birth and being small for gestational age were associated with highly increased risk of mental and developmental disorders. Mental and developmental disorders diagnosed within the first four years of life show increasing incidence rates and a complex pattern of comorbidities. Study findings point to the need of clinical and research attention towards the manifestations of developmental psychopathology in very young children.

Psychiatric Disorders in Children and Adolescents With Psychogenic Nonepileptic Seizures

OBJECTIVE

Knowledge regarding psychiatric disorders in children and adolescents with psychogenic nonepileptic seizures (PNES) is limited. This study outlines the spectrum and risk of psychiatric disorders in childhood-onset PNES.

METHODS

We performed a nationwide matched cohort study of children and adolescents with PNES 5 to 17 years of age at the time of diagnosis between January 1, 1996, and December 31, 2014. Two matched comparison groups were included: children and adolescents with epilepsy (ES) and children and adolescents without PNES or epilepsy, called healthy controls (HC). Outcomes were prevalent psychiatric disorders before index (i.e., date of diagnosis or corresponding date for HC) and incident psychiatric disorders 2 years after index. Relative risks (RRs) were calculated and adjusted for potential confounders.

RESULTS

We included 384 children and adolescents with validated PNES, 1,152 with ES, and 1,920 HC. Among the cases of PNES, 153 (39.8%) had prevalent psychiatric disorders and 150 (39.1%) had incident psychiatric disorders. Compared to the ES and HC groups, children and adolescents with PNES had elevated risks of both prevalent psychiatric disorders (adjusted RR_PNES/ES 1.87, 95% confidence interval [CI] 1.59-2.21, adjusted RR_PNES/HC 5.54, 95% CI 4.50-6.81) and incident psychiatric disorders (adjusted RR_PNES/ES 2.33, 95% CI 1.92-2.83, adjusted RR_PNES/HC 8.37, 95% CI 6.31-11.11). A wide spectrum of specific psychiatric disorders displayed elevated RRs.

CONCLUSIONS

Children and adolescents with PNES are at higher risk of a wide range of psychiatric disorders compared to children and adolescents with ES and HC. A careful psychiatric evaluation is warranted to optimize and individualize treatment.

Prenatal exposure to non-steroidal anti-inflammatory drugs and risk of attention-deficit/hyperactivity disorder: A follow-up study in the Norwegian mother, father and child cohort

PURPOSE

To estimate the association between Attention-Deficit/Hyperactivity Disorder (ADHD) in children in preschool and primary school, and prenatal exposure to non-steroidal anti-inflammatory drugs (NSAIDs) by timing and duration.

METHODS

This study was based on the Norwegian Mother, Father and Child Cohort Study linked to the Medical Birth Registry of Norway, the Norwegian Patient Registry (NPR) and the Norwegian Prescription Database (NorPD). NSAID exposure was identified by maternal self-report in pregnancy. Child diagnosis of ADHD was obtained from NPR and NorPD. Symptoms of ADHD at age 5 years were measured using Conners' Parent Rating Scale-Revised, where higher scores correspond to more symptoms. To account for time-varying exposure and confounders, marginal structural models were fitted to estimate hazard ratios and mean difference in z-scores.

RESULTS

The analyses on ADHD diagnosis and ADHD symptoms included 56 340 and 34 961 children respectively. Children exposed to NSAIDs prenatally had no increased risk of ADHD diagnosis (first trimester: HR 1.12, 95% CI 0.86;1.45, second trimester: HR 0.98, 95% CI 0.69;1.38, third trimester: HR 0.68, 95% CI 0.31; 1.46) or ADHD symptoms (first trimester: standardized mean difference 0.03, 95% CI -0.03;0.09, second trimester: standardized mean difference 0.03, 95% CI -0.04;0.11, third trimester: standardized mean difference 0.11, 95% CI -0.03; 0.25). There was no duration-response relationship for either outcome.

CONCLUSION

Though non-differential misclassification of the exposure may have attenuated results, these findings are reassuring and suggest no substantially increased risk of ADHD diagnosis or symptoms in children prenatally exposed to NSAIDs, regardless of timing or duration.

Maternal hypertensive disorders and neurodevelopmental disorders in offspring: a population-based cohort in two Nordic countries

Maternal hypertensive disorders during pregnancy (HDP) have been associated with neuropsychiatric problems in offspring. We aim to investigate the associations between specific types of maternal HDP and offspring neurodevelopmental disorders and further examine whether the timing of onset and severity of HDP would affect these associations. The study population consisted of 4,489,044 live-born singletons in Denmark during 1978–2012 and Sweden during 1987–2010. Maternal HDP was categorized into chronic hypertension, gestational hypertension, and pre-eclampsia; pre-eclampsia was further stratified according to timing (early-onset, late-onset), or severity (moderate, severe) of the disease. Neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), and intellectual disability (ID), were defined by ICD-coded register diagnosis. Cox regression was used to calculate hazard ratios (HR) while adjusting for potential confounders, and sibling analyses assessed the influence of unmeasured shared familial factors. Maternal HDP was associated with increased risks of ADHD (HR, 1.24; 95% confidence interval [CI], 1.20–1.28), ASD (1.29 [1.24–1.34]), and ID (1.58 [1.50–1.66]) in offspring, respectively, which was mostly driven by pre-eclampsia. The strongest associations were observed for early-onset and severe pre-eclampsia, and the corresponding HRs for ADHD, ASD and ID were 1.93 [1.73–2.16], 1.86 [1.61–2.15], and 3.99 [3.42–4.65], respectively. The results were similar in the sibling analyses. The associations between maternal HDP and offspring neurodevelopmental disorders were consistent across the subgroups of sex, preterm status, parity, maternal age and psychiatric disorders. Maternal HDP, especially early-onset pre-eclampsia, are associated with increased risks of ADHD, ASD, and ID in particular, independent of shared familial factors.

Maternal spontaneous abortion and the risk of attention-deficit/hyperactivity disorder in offspring: a population-based cohort study

STUDY QUESTION

Is a maternal history of spontaneous abortion (SA) associated with an increased risk of attention-deficit/hyperactivity disorder (ADHD) in offspring?

SUMMARY ANSWER

Our results suggest an association between maternal history of SA and ADHD in offspring, with the risk increasing with the number of maternal SA and highest in the firstborn children whose mothers had had recurrent SAs after adjusting for a number of potential confounders.

WHAT IS KNOWN ALREADY

A history of SA has been associated with more complications in next pregnancies and adverse childbirth outcomes, which are risk factors for ADHD in the offspring. However, no previous study has investigated whether maternal SA increases risk of ADHD in the offspring.

STUDY DESIGN, SIZE, DURATION

This population-based study included all live-born children in Denmark from 1 January 1995 to 31 December 2012 (n = 1 062 667). All children were followed from 3 years of age until the day of ADHD diagnosis, death, emigration or 31 December 2016, whichever came first.

PARTICIPANTS/MATERIALS, SETTING, METHODS

There were 130 206 (12.2%) children born to mothers who had at least one SA. Cox proportional hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

MAIN RESULTS AND THE ROLE OF CHANCE

During a median follow-up of 9.4 years (interquartile range, 5.4-14.3), 25 747 children were diagnosed with ADHD. Overall, children of mothers with a history of SA had an increased rate of ADHD (HR, 1.11; 95% CI, 1.07 to 1.15). The HRs increased with the number of maternal SA, 1.09 (95% CI, 1.05 to 1.13) for one SA and 1.22 (95% CI, 1.12 to 1.33) for at least two SAs, respectively. These findings were consistent when we took into consideration a number of factors, such as maternal socioeconomic status, type of SA, birth order, parental history of psychiatric disorders, pregnancy characteristics and adverse birth outcomes.

LIMITATIONS, REASONS FOR CAUTION

Misclassification of SA was possible as we used population-based register data to capture maternal history of SA. However, any misclassification of maternal history of SA would be non-differential with regard to the diagnosis of ADHD in offspring, which generally leads to underestimation of the associations. Furthermore, probabilistic sensitivity analysis suggested that only 1% of change in the estimate may have been due to misclassification of SA.

WIDER IMPLICATIONS OF THE FINDINGS

SA is quite frequent (varying from 15 to 20%), and a small increase of neurodevelopmental problems in offspring could have major public health implications.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the National Natural Science Foundation of China (No. 81703237, No. 81530086 and No. 81761128035), National Key Research and Development Program (2018YFC1002801, 2016YFC1000505), Shanghai Municipal Commission of Health and Family Planning (No. 2017ZZ02026, No. 2017EKHWYX-02), the Novo Nordisk Foundation (NNF18OC0052029), the Danish Council for Independent Research (DFF-6110-00019), the Nordic Cancer Union (176673, 186200 and R217-A13234-18-S65), Karen Elise Jensens Fond (2016) and Xinhua Hospital of Shanghai Jiao Tong University School of Medicine (2018YJRC03). All authors report no conflict of interest.

TRIAL REGISTRATION NUMBER

NA.

Long-term risk of epilepsy, cerebral palsy and attention-deficit/hyperactivity disorder in children affected by a threatened abortion in utero

BACKGROUND

The birth of a child affected by a threatened abortion (TAB) in utero is associated with autism spectrum disorder; association with other neurological disorders is unknown.

METHODS

This nationwide registry-based cohort study included singletons live-born in Denmark (1979-2010), followed through 2016. The outcomes were epilepsy, cerebral palsy (CP) and attention-deficit/hyperactivity disorder (ADHD). We used Cox regression to compute hazard ratios (HRs), adjusted for birth year, birth order, parental age, morbidity, medication use and maternal socio-economic factors. To remove time-invariant family-shared confounding, we applied sibling analyses.

RESULTS

The study population included 1 864 221 singletons live-born in 1979-2010. Among the TAB-affected children (N = 59 134) vs TAB-unaffected children, at the end of follow-up, the cumulative incidence was 2.2% vs 1.6% for epilepsy, 0.4% vs 0.2% for CP and 5.5% vs 4.2% for ADHD (for children born in 1995-2010). The adjusted HRs were 1.25 [95% confidence interval (CI) 1.16-1.34] for epilepsy, 1.42 (95% CI 1.20-1.68) for CP and 1.21 (95% CI 1.14-1.29) for ADHD. In the sibling design, the adjusted HRs were unity for epilepsy (full siblings: 0.96, 95% CI 0.82-1.12; maternal: 1.04, 95% CI 0.90-1.20; paternal: 1.08, 95% CI 0.93-1.25) and ADHD (full: 1.08, 95% CI 0.92-1.27; maternal: 1.04, 95% CI 0.90-1.20; paternal: 1.08, 95% CI 0.93-1.25). For CP, HRs shifted away from unity among sibling pairs (full: 2.92, 95% CI 1.33-6.39; maternal: 2.03, 95% CI 1.15-3.57; paternal: 3.28, 95% CI 1.36-7.91).

CONCLUSIONS

The birth of a child affected by TAB in utero was associated with a greater risk of CP, but not epilepsy or ADHD.

The validity of child and adolescent depression diagnoses in the Danish psychiatric central research register

OBJECTIVE

This study examined the validity of childhood depression diagnoses in the Danish Psychiatric Central Research Register (DPCRR) and identified predictors of validity.

METHODS

A nationwide random sample of 500 children (6-17 years) diagnosed with depression between 1996 and 2016 was identified in the DPCRR. Psychiatric hospital records were reviewed and rated using an online checklist. The primary outcome was whether depressive symptoms and functional impairment documented in hospital records justified a depressive disorder diagnosis based on ICD-10 or DSM-5 diagnostic criteria. Diagnostic validity was calculated as the positive predictive value. Binary logistic regression analysis was used to identify potential predictors of diagnostic validity, and these were included in a multiple logistic regression.

RESULTS

Psychiatric hospital records were available for 393 patients (78.6%). The documentation in the records justified an ICD-10 depressive episode diagnosis in 72.8%, and DSM-5 major depressive disorder in 73.3% of the patients registered with a depression diagnosis. We identified three predictors of diagnostic validity: (i) The validity increased almost linearly from 2000 to 2016 (OR 1.14, 95% CI 1.07-1.20, p < 0.001), (ii) antidepressant use was associated with increased diagnostic validity (OR 2.27, 95% CI 1.35-3.82, p = 0.002) and (iii) emergency department admission predicted low diagnostic validity (OR 0.33, 95% CI 0.12-0.93, p = 0.036).

CONCLUSION

Childhood depression diagnoses registered in the DPCRR show a satisfactory validity according to both ICD-10 and DSM-5 diagnostic criteria. Diagnostic validity increased steadily from 2000 to 2016 and was positively correlated with antidepressant use. Depression diagnoses assigned in emergency departments had low diagnostic validity.

Time trends in treatment modes of anorexia nervosa in a nationwide cohort with free and equal access to treatment

BACKGROUND

Treating patients with anorexia nervosa (AN) remains a major challenge. The choice between an inpatient or an outpatient care setting is an essential issue for the patients and for their relatives with major health economic implications. However, health services-related studies are lacking. The present study was a descriptive exploration of time-trends in treatment modes of patients with free and equal access to health services.

METHODS

The study was based on a nationwide cohort of patients diagnosed for the first time with AN, each followed for 5 years in the registers covering the years 1994-2018. The per patient number of hospital admissions, cumulated number of days of hospitalization and number of outpatient visits during the first 5 years after initial diagnosis were considered.

RESULTS

The cohort of patients with AN with at least 5 years of follow-up amounted to N = 7,505. A clear trend was observed in the per patient five-year cumulated number of inpatient days, decreasing by 6% per year after adjustment for age at diagnosis, parental mental diagnosis, and family income. The five-year number of hospital admissions after initial diagnosis decreased by 2% per year, while no trend was observed for outpatient visits.

CONCLUSIONS

The per patient number of hospitalizations and cumulated days of hospitalization during 5 years after diagnosis were reduced for patients initially diagnosed with AN while there was no change in the number of outpatient visits. The factors contributing to these changes of treatment modes over time are in need of further study.

The Association between Residential Green Space in Childhood and Development of Attention Deficit Hyperactivity Disorder: A Population-Based Cohort Study

BACKGROUND

Access to green space has been hypothesized to have a beneficial impact on children's mental well-being and cognitive development. The underlying mechanisms of the mental health benefits of green space are not fully understood, but different pathways have been suggested, such as the psychologically restoring capacities of green space, the ability to facilitate physical activity and social cohesion, and the mitigation of exposure to air pollution.

OBJECTIVES

In this nationwide cohort study, we investigated associations between residential green space in early childhood and a clinical diagnosis of attention deficit hyperactivity disorder (ADHD).

METHODS

The cohort included individuals, who were born in Denmark between 1992 and 2007 (n=814,689) and followed for a diagnosis of ADHD from age 5, during the period 1997-2016. We used the normalized difference vegetation index (NDVI) as a measure of vegetation greenness surrounding each residential address in a quadratic area of 210m×210m in which the residence was located in the center of the quadrate. Individual exposure to green space was calculated as the average of NDVI surrounding each individual's residential address (or addresses if more than one) between birth and the fifth birthday. Multilevel modeling was used to estimate the incidence rate ratios (IRRs) with 95% confidence intervals (CI) for ADHD, according to exposure level and adjusted for calendar time, age, sex, parental socioeconomic status, neighborhood level socioeconomic status, and urbanicity.

RESULTS

Individuals living in areas defined by sparse green vegetation (lowest decile of NDVI) had an increased risk of developing ADHD, compared with individuals living in areas within the highest decile of NDVI (IRR=1.55; 95% CI: 1.46, 1.65). Adjusting for the known confounders attenuated the result, but the association remained (IRR=1.20; 95% CI: 1.13, 1.28).

CONCLUSION

Our findings suggest that lower levels of green space in residential surroundings, during early childhood, may be associated with a higher risk of developing ADHD. https://doi.org/10.1289/EHP6729.

School performance, psychiatric comorbidity, and healthcare utilization in pediatric multiple sclerosis: A nationwide population-based observational study

Background:

Pediatric multiple sclerosis (MS) may hamper educational achievements due to psychiatric comorbidity and cognitive impairment. Our aims were to investigate school performance, psychiatric comorbidity, and healthcare utilization following pediatric MS and to differentiate between disability in MS and that arising from a non-brain-related chronic disease.

Methods:

We included all children (<18 years) with MS onset during 2008–2015 in Denmark with a medical record–validated MS diagnosis. The control groups were children from the general population or children with non-brain-related chronic diseases. Outcomes were register-based on 9–12 grade point average, psychiatric comorbidity, and healthcare visits.

Results:

Cohorts were children with MS ( n = 92), control children matched to children with MS ( n = 920), children with non-brain-related chronic diseases ( n = 9108), and “healthy” children with neither MS nor brain-related chronic disease ( n = 811,464). School performance in grades 9–12 was similar, but children with MS compared to those with non-brain-related chronic disease had an almost doubled hazard for psychiatric comorbidity (hazard ratio = 1.87; 95% confidence interval = 1.38–2.53; p < 0.0001) and a higher rate of all hospital visits ( p < 0.0001) but a lower rate of hospital admissions ( p = 0.001).

Conclusion:

Children with MS have a seemingly standard school performance but increased psychiatric comorbidity and a high rate of healthcare utilization.

Exposure to Manganese in Drinking Water during Childhood and Association with Attention-Deficit Hyperactivity Disorder: A Nationwide Cohort Study

BACKGROUND

Manganese (Mn) in drinking water may increase the risk of several neurodevelopmental outcomes, including attention-deficit hyperactivity disorder (ADHD). Earlier epidemiological studies on associations between Mn exposure and ADHD-related outcomes had small sample sizes, lacked spatiotemporal exposure assessment, and relied on questionnaire data (not diagnoses)-shortcomings that we address here.

OBJECTIVE

Our objective was to assess the association between exposure to Mn in drinking water during childhood and later development of ADHD.

METHODS

In a nationwide population-based registry study in Denmark, we followed a cohort of 643,401 children born 1992-2007 for clinical diagnoses of ADHD. In subanalyses, we classified cases into ADHD-Inattentive and ADHD-Combined subtypes based on hierarchical categorization of International Classification of Diseases (ICD)-10 codes. We obtained Mn measurements from 82,574 drinking water samples to estimate longitudinal exposure during the first 5 y of life with high spatiotemporal resolution. We modeled exposure as both peak concentration and time-weighted average. We estimated sex-specific hazard ratios (HRs) in Cox proportional hazards models adjusted for age, birth year, socioeconomic status (SES), and urbanicity.

RESULTS

We found that exposure to increasing levels of Mn in drinking water was associated with an increased risk of ADHD-Inattentive subtype, but not ADHD-Combined subtype. After adjusting for age, birth year, and SES, females exposed to high levels of Mn (i.e., >100μg/L) at least once during their first 5 y of life had an HR for ADHD-Inattentive subtype of 1.51 [95% confidence interval (CI): 1.18, 1.93] and males of 1.20 (95% CI: 1.01, 1.42) when compared with same-sex individuals exposed to <5μg/L. When modeling exposure as a time-weighted average, sex differences were no longer present.

DISCUSSION

Mn in drinking water was associated with ADHD, specifically the ADHD-Inattentive subtype. Our results support earlier studies suggesting a need for a formal health-based drinking water guideline value for Mn. Future Mn-studies should examine ADHD subtype-specific associations and utilize direct subtype measurements rather than relying on ICD-10 codes alone. https://doi.org/10.1289/EHP6391.

Association of Mental Disorder in Childhood and Adolescence With Subsequent Educational Achievement

IMPORTANCE

Onset of mental disorders during childhood or adolescence has been associated with underperformance in school and impairment in social and occupational life in adulthood, which has important implications for the affected individuals and society.

OBJECTIVE

To compare the educational achievements at the final examination of compulsory schooling in Denmark between individuals with and those without a mental disorder.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study was conducted in Denmark and obtained data from the Danish Civil Registration System and other nationwide registers. The 2 cohorts studied were (1) all children who were born in Denmark between January 1, 1988, and July 1, 1999, and were alive at age 17 years (n = 629 622) and (2) all children who took the final examination at the end of ninth grade in both Danish and mathematics subjects between January 1, 2002, and December 31, 2016 (n = 542 500). Data analysis was conducted from March 1, 2018, to March 1, 2019.

EXPOSURES

Clinical diagnosis by a psychiatrist of any mental disorder or 1 of 29 specific mental disorders before age 16 years.

MAIN OUTCOMES AND MEASURES

Taking the final examination at the end of ninth grade and mean examination grades standardized as z scores with differences measured in SDs (standardized mean grade difference).

RESULTS

Of the total study population (n = 629 622; 306 209 female and 323 413 male), 523 312 individuals (83%) took the final examination before 17 years of age and 38 001 (6%) had a mental disorder before that age. Among the 542 500 individuals (274 332 female and 268 168 male), the mean (SD) age was 16.1 (0.33) years for the females and 16.2 (0.34) years for the males. Among the 15 843 female and 22 158 male students with a mental disorder, a lower proportion took the final examination (0.52; 95% CI, 0.52-0.53) compared with individuals without a mental disorder (0.88; 95% CI, 0.88-0.88). Mental disorders affected the grades of male individuals (standardized mean grade difference, -0.30; 95% CI, -0.32 to -0.28) more than the grades of their female peers (standardized mean grade difference, -0.24; 95% CI, -0.25 to -0.22) when compared with same-sex individuals without mental disorders. Most specific mental disorders were associated with statistically significantly lower mean grades, with intellectual disability associated with the lowest grade in female and male students (standardized mean grade difference, -1.07 [95% CI, -1.23 to -0.91] and -1.03 [95% CI, -1.17 to -0.89]; P = .76 for sex differences in the mean grades). Female and male students with anorexia nervosa achieved statistically significantly higher grades on the final examination (standardized mean grade difference, 0.38 [95% CI, 0.32-0.44] and 0.31 [95% CI, 0.11-0.52]; P = .54 for sex differences in the mean grades) compared with their peers without this disorder. For those with anxiety, attachment, attention-deficit/hyperactivity, and other developmental disorders, female individuals attained relatively lower standardized mean grades compared with their male counterparts.

CONCLUSIONS AND RELEVANCE

Results of this study suggest that, in Denmark, almost all mental disorders in childhood or adolescence may be associated with a lower likelihood of taking the final examination at the end of ninth grade; those with specific disorders tended to achieve lower mean grades on the examination; and female, compared with male, individuals with certain mental disorders appeared to have relatively more impairment. These findings appear to emphasize the need to provide educational support to young people with mental disorders.

Genetic liability to ADHD and substance use disorders in individuals with ADHD

AIMS

1) To investigate whether genetic liability to attention-deficit/hyperactivity disorder (ADHD), indexed by polygenic risk scores for ADHD (PRS-ADHD), is associated with substance use disorders (SUD) in individuals with ADHD. 2) To investigate whether other individual- or family-related risk factors for SUD could mediate or confound this association.

DESIGN

Population-based cohort study SETTING AND PARTICIPANTS: ADHD cases in the iPSYCH sample (a Danish case-cohort sample of genotyped cases with specific mental disorders), born in Denmark between 1981 and 2003 (N = 13 116). Register-based information on hospital diagnoses of SUD was available until December 31, 2016.

MEASUREMENTS

We estimated odds ratios (ORs) with 95% confidence intervals (CIs) for any SUD as well as for different SUD types (alcohol, cannabis, and other illicit drugs) and severities (use, abuse, and addiction), with effect sizes corresponding to a comparison of the highest PRS-ADHD decile to the lowest.

FINDINGS

PRS-ADHD were associated with any SUD (OR = 1.30, 95% CI: 1.11-1.51). Estimates were similar across different types and severity levels of SUD. Other risk factors for SUD (male sex, age at ADHD diagnosis, comorbid conduct problems, and parental factors including SUD, mental disorders, and socio-economic status) were independently associated with increased risk of SUD. PRS-ADHD explained a minor proportion of the variance in SUD (0.2% on the liability scale) compared to the other risk factors. The association between PRS-ADHD and any SUD was slightly attenuated (OR = 1.21, 95% CI: 1.03-1.41) after adjusting for the other risk factors for SUD. Furthermore, associations were nominally higher in females than in males (ORfemales  = 1.59, 95% CI: 1.19-2.12, ORmales  = 1.18, 95% CI: 0.98-1.42).

CONCLUSIONS

A higher genetic liability to attention-deficit/hyperactivity disorder appears to be associated with higher risks of substance use disorders in individuals with attention-deficit/hyperactivity disorder.

Prevalence of mental disorders in children and adolescents with cerebral palsy: Danish nationwide follow-up study

AIM

To compare the prevalence of mental disorders (MDs) in a cohort of children and adolescents with and without cerebral palsy (CP) and to explore whether there is an association between MDs and the Gross Motor Function Classification System (GMFCS) level.

METHOD

A register-linkage follow-up study of 10- to 16-year children with CP (identified in the Danish National Cerebral Palsy Registry, n = 893), and 2627 children without CP, matched by gender and age. Information on MDs was obtained from the National Patient Registry in Denmark and based on ICD-10-codes. Conditional logistic regression was performed in order to compare the prevalence of MDs.

RESULTS

The prevalence of MDs was significantly higher in children and adolescents with CP (22.4%, CI 19.8-25.2%) compared with controls (6.3%, CI 5.5-7.3%). Intellectual disability was statistically significantly associated with motor function (odds ratio (OR) 4.55, CI 2.81-7.36 for GMFCS levels IV-V compared to GMFCS level I), but there were no statistically significant association between motor function and autism spectrum disorders, ADHD or affective disorders.

INTERPRETATION

Our findings emphasize that follow-up of children with CP should include screening for both cognitive dysfunction and other mental disorders. The motor function does not predict the risk of other mental disorders than intellectual disability in children and adolescents with CP.

Cumulative incidence and relative risk of sleep problems among children and adolescents with newly diagnosed neurodevelopmental disorders: A nationwide register-based study

We estimated the absolute and relative risk of sleep problems in children and adolescents with newly diagnosed neurodevelopmental disorders. This was a population-based cohort study of individuals born in Denmark in 1993-2014 and followed in nationwide registers in 2011-2016. We estimated the 5-year cumulative incidence of sleep problems in incident cases of attention-deficit/hyperactivity disorder (ADHD; n = 12,844), autism spectrum disorder (ASD; n = 8,073), oppositional defiant disorder/conduct disorder (ODD/CD; n = 2,234) and epilepsy (n = 3,709). Hazard ratios (HRs) for sleep problems were estimated by Cox regression. The 5-year risk of sleep problems was highest in ADHD (29.2%; 95% CI, 28.4-30.1), ASD (24.2%; 95% CI, 23.1-25.3) and ODD/CD (27.1% 95% CI, 25.0%-29.2%) and lowest in epilepsy (11.3%; 95% CI, 10.2%-12.6%). For ADHD and ASD, sleep problems were more common in females than in males. Furthermore, sleep problems were predicted by high parental socioeconomic status and varied with the geographical region of residence, suggesting that different clinical practices exist across Denmark and that sleep problems may be more likely to go undetected in families of lower socioeconomic position. Compared with individuals without these disorders, the likelihood of sleep problems was increased in individuals with ADHD (HR, 33.81; 95% CI, 32.78-34.87), ASD (HR, 16.77; 95% CI, 16.15-17.41), ODD/CD (HR, 14.73; 95% CI, 13.88-15.64) and epilepsy (HR, 6.01; 95% CI, 5.67-6.37). After mutual adjustment for comorbidity, HRs were attenuated, especially in ASD, ODD/CD and epilepsy when adjusted for ADHD, suggesting that the increased risk of sleep problems in individuals with ASD, ODD/CD and epilepsy is driven largely by comorbid ADHD.

Obstetric oxytocin exposure and ADHD and ASD among Danish and Finnish children

Background

Some studies have indicated an increased risk of attention deficit hyperactivity disorder (ADHD) and a small, sex-specific association with autism spectrum disorder (ASD) among children prenatally exposed to obstetric oxytocin. Since oxytocin is widely used in the obstetric ward, these potentially deleterious effects are of concern. Thus, we aimed to examine whether obstetric oxytocin treatment for labour induction or augmentation is associated with ADHD and ASD in offspring born in a two-country design based on data from Denmark and Finland.

Methods

This population-based study used data from national registers in Denmark and Finland. Singletons born in Denmark 2000–10 (n = 577 380) and Finland 1991–2010 (n = 945 543), who survived infancy, were followed until 31 December 2015. ADHD and ASD were defined using diagnostic codes. For ADHD, we also included information on prescribed and redeemed ADHD medication in the definition. Hazards ratios (HRs) with 95% confidence intervals (CI), modelled with age as the underlying time scale, were calculated to estimate the associations.

Results

Oxytocin was used in 31% and 46% of the included deliveries in Denmark and Finland, respectively. In crude analyses, prenatal oxytocin was associated with an approximately 20% increased risk of ADHD and ASD, but confounder adjustment attenuated the association. The adjusted HR was 1.03, 95% CI 1.01–1.05, for ADHD and 1.05, 95% CI 1.02–1.08, for ASD. The results were similar in across country and gender.

Conclusions

We found an association between synthetic oxytocin and ADHD or ASD which is unlikely to reflect a causal association and thus should not support the concern of clinical use. Our results help to allay concerns of obstetric use of oxytocin causing ADHD or ASD.

Exposure to air pollution in early childhood and the association with Attention-Deficit Hyperactivity Disorder

BACKGROUND

Exposure to air pollution in early life has been linked to cognitive deficits and adverse neurodevelopmental effects. However, studies examining associations between air pollutants and Attention-Deficit/Hyperactivity Disorder (ADHD) have had conflicting findings.

METHODS

Individuals born in Denmark 1992-2007 (n = 809,654) were followed for the development of ADHD from 1997 to 2013. Data on daily concentrations of nitrogen dioxide (NO₂) and fine particulate matter (PM_2.5) from air-modeling data at a 1 km × 1 km resolution at residences within the first five years of life, was linked with population-based data from the Danish national registers, including data on clinical diagnoses of ADHD. We estimated incidence rate ratios (IRRs) with 95% confidence intervals (CI) for ADHD, according to increases in exposures, adjusting for age, year, sex, and parental education and income.

RESULTS

Exposure to NO₂ and PM_2.5 during early life was associated with a significantly increased risk of ADHD: IRR of 1.38 (Cl: 1.35 to 1.42) per 10 μg/m³ increase in NO₂ and an IRR of 1.51 (Cl: 1.41 to 1.62) per 5 μg/m³ increase in PM_2.5. In two-pollutant models, the association between NO₂ and ADHD did not change (IRR 1.35; 95% CI: 1.31 to 1.39), while the association with PM_2.5 was substantially attenuated (IRR 1.07; 95% CI: 0.98 to 1.16), although in stratified models an elevated association with PM_2.5 was found in the lowest quintile of NO₂ exposure.

CONCLUSIONS

In this large nationwide prospective cohort study, residential air pollution exposure, specifically NO₂, during early childhood was associated with the development of ADHD, even when adjusted for parental level of income and education.

Incidence Rates and Cumulative Incidences of the Full Spectrum of Diagnosed Mental Disorders in Childhood and Adolescence

IMPORTANCE

Knowledge about the epidemiology of mental disorders in children and adolescents is essential for research and planning of health services. Surveys can provide prevalence rates, whereas population-based registers are instrumental to obtain precise estimates of incidence rates and risks.

OBJECTIVE

To estimate age- and sex-specific incidence rates and risks of being diagnosed with any mental disorder during childhood and adolescence.

DESIGN

This cohort study included all individuals born in Denmark from January 1, 1995, through December 31, 2016 (1.3 million), and followed up from birth until December 31, 2016, or the date of death, emigration, disappearance, or diagnosis of 1 of the mental disorders examined (14.4 million person-years of follow-up). Data were analyzed from September 14, 2018, through June 11, 2019.

EXPOSURES

Age and sex.

MAIN OUTCOMES AND MEASURES

Incidence rates and cumulative incidences of all mental disorders according to the ICD-10 Classification of Mental and Behavioral Disorders: Diagnostic Criteria for Research, diagnosed before 18 years of age during the study period.

RESULTS

A total of 99 926 individuals (15.01%; 95% CI, 14.98%-15.17%), including 41 350 girls (14.63%; 95% CI, 14.48%-14.77%) and 58 576 boys (15.51%; 95% CI, 15.18%-15.84%), were diagnosed with a mental disorder before 18 years of age. Anxiety disorder was the most common diagnosis in girls (7.85%; 95% CI, 7.74%-7.97%); attention-deficit/hyperactivity disorder (ADHD) was the most common in boys (5.90%; 95% CI, 5.76%-6.03%). Girls had a higher risk than boys of schizophrenia (0.76% [95% CI, 0.72%-0.80%] vs 0.48% [95% CI, 0.39%-0.59%]), obsessive-compulsive disorder (0.96% [95% CI, 0.92%-1.00%] vs 0.63% [95% CI, 0.56%-0.72%]), and mood disorders (2.54% [95% CI, 2.47%-2.61%] vs 1.10% [95% CI, 0.84%-1.21%]). Incidence peaked earlier in boys than girls in ADHD (8 vs 17 years of age), intellectual disability (5 vs 14 years of age), and other developmental disorders (5 vs 16 years of age). The overall risk of being diagnosed with a mental disorder before 6 years of age was 2.13% (95% CI, 2.11%-2.16%) and was higher in boys (2.78% [95% CI, 2.44%-3.15%]) than in girls (1.45% [95% CI, 1.42%-1.49%]).

CONCLUSIONS AND RELEVANCE

This nationwide population-based cohort study provides a first comprehensive assessment of the incidence and risks of mental disorders in childhood and adolescence. By 18 years of age, 15.01% of children and adolescents in this study were diagnosed with a mental disorder. The incidence of several neurodevelopmental disorders peaked in late adolescence in girls, suggesting possible delayed detection. The distinct signatures of the different mental disorders with respect to sex and age may have important implications for service planning and etiological research.