Demographic Characteristics and Psychiatric Comorbidity of Children and Adolescents Diagnosed with ADHD in Specialized Healthcare

Parental psychopathology and offspring anxiety disorders in childhood and adolescence: A Finnish nationwide register study

BACKGROUND

Research suggests an association between parental psychiatric disorders and offspring anxiety disorders, yet comprehensive studies are limited. This study aims to investigate the associations between various parental psychiatric disorders and anxiety disorders in their offspring.

METHOD

Using Finnish register data, this nested case-control study analyzed 867,175 singleton live births from 1992 to 2006, identifying 21,671 cases of anxiety disorders diagnosed between 1998 and 2016. Matched with four controls each (n = 72,414) based on age and biological sex, the study adjusted for demographic and prenatal factors using conditional logistic regression models to calculate odds ratios (aORs).

RESULTS

There was a significant association between parental psychiatric disorders and increased risk of anxiety disorders in offspring. The risk was notably higher when both parents had psychiatric disorders (aOR = 5.04; 95 % CI, 4.70-5.39; p < .001). Maternal psychiatric disorders were strongly associated with offspring anxiety than paternal disorders (aOR 1.52; 95 % CI 1.43-1.61; p < .001). This association was consistent regardless of timing of parental diagnosis. Significant associations were observed between any parental psychiatric disorder and increased risks in offspring for specific phobia, social phobia, generalized anxiety disorder, separation anxiety, and panic disorder. Maternal psychiatric disorders showed elevated risk for panic disorder and social phobia among girls and separation anxiety and generalized anxiety among boys.

CONCLUSION

The findings emphasize the significant impact of parental psychiatric health on offspring anxiety disorders, highlighting the influence of genetic and environmental factors. Addressing parental mental health is crucial in preventing childhood anxiety disorders.

Metalinguistic and Reading Skills in a Sample of Colombian Children with Attention Deficit Hyperactivity Disorder

Objective: This study aimed to examine metalinguistic skills and reading processes in children diagnosed with ADHD, compared to a matched control group. Method: An explanatory experimental design was employed, involving a sample of 194 children from Manizales, comprising 97 children diagnosed with ADHD and 97 controls. The study utilized tasks from the Children's Neuropsychological Assessment (CNA) protocol to assess metalinguistic and reading abilities. Results: Children with ADHD exhibited significantly lower performance across all metalinguistic and reading tasks compared to the control group, except for spelling and silent reading comprehension tasks. Conclusions: These findings corroborate previous research conducted in Manizales, underscoring the specific challenges in metalinguistic and reading domains among children with ADHD. Future research should explore the influence of working memory on phonological awareness and its implications for metalinguistic skills and reading development.

Child- and parent-related determinants for out-of-home care in a nationwide population with neurodevelopmental disorders: a register-based Finnish birth cohort 1997 study

Neurodevelopmental disorders (NDDs) are among the most common health issues in childhood and adolescence. Psychiatric disorders are known to be overrepresented among children using child welfare services and placed in out-of-home care (OHC). Child- and parent-related determinants for OHC among a national population with NDDs were evaluated utilising longitudinal register data from the national Finnish Birth Cohort 1997 (n = 58,802) from birth to 18 years (1997-2015). The cohort members with NDDs (n = 5,143, 9% of total cohort) formed our study population. Based on their history of OHC, cohort members with NDD were categorised to OHC (n = 903) and non-OHC groups (n = 4,240). Of all cohort members with NDDs, 17.6% had a history of OHC. Within NDDs, a significant excess of ADHD diagnosis was observed in the OHC group compared to the non-OHC group (49% vs. 26%). The OHC group with NDDs was significantly characterised by having comorbid psychiatric diagnosis for conduct and oppositional disorders (adj. RR 2.21), substance use disorders (adj. RR 1.61) and depression and anxiety disorders (adj. RR 1.60). Of all parent-related determinants, the most prevailing in the OHC group compared to the non-OHC group, was social assistance received by parent (88% vs. 44.5%). The longer the period (in years) for received social assistance, the greater the likelihood for OHC (adj. RRs range from 2.41 for one year to 5.24 for over 4 years). Further, significantly associating determinants for OHC were parental psychiatric disorders (adj. RR 1.42) and parental death (adj. RR 1.23). Our findings from the population-based cohort of children and adolescents with NDDs highlight the importance of screening and assessment of family situation. Also, effective prevention and treating of comorbid psychiatric disorders, especially conduct and oppositional disorders is essential.

Selective mutism and the risk of mental and neurodevelopmental disorders among siblings

The siblings of children with mental disorders are more likely to experience mental health issues themselves, but there has been a lack of sibling studies on selective mutism (SM). The aim of this population-based study was to use national registers to examine associations between children with SM and diagnoses of various mental disorder in their siblings. All singleton children born in Finland from 1987 to 2009, and diagnosed with SM from 1998 to 2012, were identified from national health registers and matched with four controls by age and sex. Their biological siblings and parents were identified using national registries and the diagnostic information on the siblings of the subjects and controls was obtained. The final analyses comprised 658 children with SM and their 1661 siblings and 2092 controls with 4120 siblings. The analyses were conducted using generalized estimating equations. Mental disorders were more common among the siblings of the children with SM than among the siblings of the controls. The strongest associations were observed for childhood emotional disorders and autism spectrum disorders after the data were adjusted for covariates and comorbid diagnoses among SM subjects. The final model showed associations between SM and a wide range of disorders in siblings, with strongest associations with disorders that usually have their onset during childhood. Our finding showed that SM clustered with other mental disorders in siblings and this requires further research, especially the association between SM and autism spectrum disorders. Strong associations with childhood onset disorders may indicate shared etiologies.

Maternal exposure to childhood maltreatment and mental and behavioral disorders in children

Exposure to maltreatment in childhood is associated with lifelong risk of mental and behavioral disorders. Whether the effects extend to the next generation remains unclear. We examined whether maternal exposure to childhood abuse and neglect in her own childhood were associated with mental and behavioral disorders and psychiatric symptoms in her children, and whether maternal lifetime mental and behavioral disorders or lower education level mediated or added to the effects. Mothers (n = 2252) of the Prediction and Prevention of Preeclampsia and Intrauterine Growth Restriction cohort study completed the Childhood Trauma Questionnaire and reported on their education and their 7.0-12.1-year-old children's psychiatric symptoms using the Strengths and Difficulties Questionnaire. We identified lifetime mental and behavioral disorder diagnoses for the mothers and diagnoses for their children from birth (2006-2010) until 8.4-12.8 years (12/31/2018) from Care Register for Health Care. We found that maternal exposure to childhood abuse, but not neglect, was associated with higher hazards of mental and behavioral disorders (hazard ratio 1.20, 95% confidence interval 1.06-1.37) in children. These associations were partially mediated by maternal mental and behavioral disorders and education (proportion of effect size mediated: 23.8% and 15.1%, respectively), which together with maternal exposure to childhood abuse added to the hazard of mental and behavioral disorders in children. Similar associations were found for maternal exposure to childhood abuse and neglect with psychiatric symptoms in children. To conclude, maternal exposure to childhood maltreatment is associated with mental and behavioral disorders and psychiatric symptoms in children. Our findings call for interventions to prevent intergenerational transmission.

An updated safety review of the current drugs for managing ADHD in children

INTRODUCTION

Attention-Deficit/Hyperactivity Disorder (ADHD) is a highly prevalent condition that causes persistent problems with attention and/or hyperactivity-impulsivity and often results in significant impairment when left untreated. Medications for this disorder continue to evolve and provide new treatment options. Ongoing review of related medication safety and tolerability remains an important task for prescribers.

AREAS COVERED

This manuscript provides an updated safety review of medications used to treat ADHD in children and adolescents. PubMed and OneSearch online databases were utilized to search for literature relevant to the topic of ADHD medications and safety. Clinical trials of medications used to treat ADHD, systematic reviews and meta-analyses, and articles covering specific safety issues (adverse or unfavorable events) such as cardiovascular effects, seizures, impact on growth, depression, suicidal ideation, substance use disorders, psychosis, and tics are described.

EXPERT OPINION

Available pharmacologic treatments for ADHD have favorable efficacy, safety and tolerability and allow many patients to achieve significant improvement of their symptoms. Despite the availability of multiple stimulant and non-stimulant formulations, some individuals with ADHD may not tolerate available medications or attain satisfactory improvement. To satisfy unmet clinical needs, ADHD pharmaceutical research with stimulant and nonstimulant formulations targeting dopamine, norepinephrine, and novel receptors is ongoing.

In silico evaluation of the role of lisdexamfetamine on attention-deficit/hyperactivity disorder common psychiatric comorbidities: mechanistic insights on binge eating disorder and depression

Attention-deficit/hyperactivity disorder (ADHD) is a psychiatric condition well recognized in the pediatric population that can persist into adulthood. The vast majority of patients with ADHD present psychiatric comorbidities that have been suggested to share, to some extent, the pathophysiological mechanism of ADHD. Lisdexamfetamine (LDX) is a stimulant prodrug approved for treating ADHD and, in the US, also for binge eating disorder (BED). Herein, we evaluated, through a systems biology-based in silico method, the efficacy of a virtual model of LDX (vLDX) as ADHD treatment to improve five common ADHD psychiatric comorbidities in adults and children, and we explored the molecular mechanisms behind LDX's predicted efficacy. After the molecular characterization of vLDX and the comorbidities (anxiety, BED, bipolar disorder, depression, and tics disorder), we created a protein-protein interaction human network to which we applied artificial neural networks (ANN) algorithms. We also generated virtual populations of adults and children-adolescents totaling 2,600 individuals and obtained the predicted protein activity from Therapeutic Performance Mapping System models. The latter showed that ADHD molecular description shared 53% of its protein effectors with at least one studied psychiatric comorbidity. According to the ANN analysis, proteins targeted by vLDX are predicted to have a high probability of being related to BED and depression. In BED, vLDX was modeled to act upon neurotransmission and neuroplasticity regulators, and, in depression, vLDX regulated the hypothalamic-pituitary-adrenal axis, neuroinflammation, oxidative stress, and glutamatergic excitotoxicity. In conclusion, our modeling results, despite their limitations and although requiring in vitro or in vivo validation, could supplement the design of preclinical and potentially clinical studies that investigate treatment for patients with ADHD with psychiatric comorbidities, especially from a molecular point of view.

Maternal SSRI use during pregnancy and offspring depression or anxiety disorders: A review of the literature and description of a study protocol for a register-based cohort study

Previous studies examining the relationship between in utero exposure to selective serotonin reuptake inhibitors (SSRI) and long-term offspring depressive or anxiety behaviors are inconclusive. We aimed to critically review the findings of previous studies and describe a new study protocol to investigate the association of prenatal SSRI exposure and offspring depression or anxiety using data from several Finnish national registers. The study includes 1,266,473 mothers and their live-born singleton offspring, born in 1996-2018. The study cohorts include the prenatally SSRI exposed group and three comparison groups: 1) depression exposed/antidepressants unexposed, 2) unexposed to antidepressants or antipsychotics and depression, and 3) discordant siblings. We aim to examine whether depression in prenatally SSRI exposed children is more common or severe than depression in the offspring of mothers with depression but without SSRI exposure. We aim to disambiguate the effects of maternal SSRI from the effects of maternal depression, severity of maternal depression and familial loading history of psychiatric disorders by including data from first-degree relatives of prenatally SSRI exposed and unexposed children. Associations between exposure and outcome are assessed by statistical modeling, accounting for within-family correlation. The study has potential public health significance and in guiding clinicians in considering treatment options for pregnant women.

ADHD symptoms and diagnosis in adult preterms: systematic review, IPD meta-analysis, and register-linkage study

BACKGROUND

This study examined differences in ADHD symptoms and diagnosis between preterm and term-born adults (≥18 years), and tested if ADHD is related to gestational age, birth weight, multiple births, or neonatal complications in preterm borns.

METHODS

(1) A systematic review compared ADHD symptom self-reports and diagnosis between preterm and term-born adults published in PubMed, Web of Science, and PROQUEST until April 2021; (2) a one-stage Individual Participant Data(IPD) meta-analysis (n = 1385 preterm, n = 1633 term; born 1978-1995) examined differences in self-reported ADHD symptoms[age 18-36 years]; and (3) a population-based register-linkage study of all live births in Finland (01/01/1987-31/12/1998; n = 37538 preterm, n = 691,616 term) examined ADHD diagnosis risk in adulthood (≥18 years) until 31/12/2016.

RESULTS

Systematic review results were conflicting. In the IPD meta-analysis, ADHD symptoms levels were similar across groups (mean z-score difference 0.00;95% confidence interval [95% CI] -0.07, 0.07). Whereas in the register-linkage study, adults born preterm had a higher relative risk (RR) for ADHD diagnosis compared to term controls (RR = 1.26, 95% CI 1.12, 1.41, p < 0.001). Among preterms, as gestation length (RR = 0.93, 95% CI 0.89, 0.97, p < 0.001) and SD birth weight z-score (RR = 0.88, 95% CI 0.80, 0.97, p < 0.001) increased, ADHD risk decreased.

CONCLUSIONS

While preterm adults may not report higher levels of ADHD symptoms, their risk of ADHD diagnosis in adulthood is higher.

IMPACT

Preterm-born adults do not self-report higher levels of ADHD symptoms, yet are more likely to receive an ADHD diagnosis in adulthood compared to term-borns. Previous evidence has consisted of limited sample sizes of adults and used different methods with inconsistent findings. This study assessed adult self-reported symptoms across 8 harmonized cohorts and contrasted the findings with diagnosed ADHD in a population-based register-linkage study. Preterm-born adults may not self-report increased ADHD symptoms. However, they have a higher risk of ADHD diagnosis, warranting preventive strategies and interventions to reduce the presentation of more severe ADHD symptomatology in adulthood.

Comparison of new psychiatric diagnoses among Finnish children and adolescents before and during the COVID-19 pandemic: A nationwide register-based study

BACKGROUND

Coronavirus Disease 2019 (COVID-19) restrictions decreased the use of specialist psychiatric services for children and adolescents in spring 2020. However, little is known about the pattern once restrictions eased. We compared new psychiatric diagnoses by specialist services during pandemic and pre-pandemic periods.

METHODS AND FINDINGS

This national register study focused on all Finnish residents aged 0 to 17 years from January 2017 to September 2021 (approximately 1 million a year). The outcomes were new monthly diagnoses for psychiatric or neurodevelopmental disorders in specialist services. These were analyzed by sex, age, home location, and diagnostic groups. The numbers of new diagnoses from March 2020 were compared to predictive models based on previous years. The predicted and observed levels in March to May 2020 showed no significant differences, but the overall difference was 18.5% (95% confidence interval 12.0 to 25.9) higher than predicted in June 2020 to September 2021, with 3,821 more patients diagnosed than anticipated. During this period, the largest increases were among females (33.4%, 23.4 to 45.2), adolescents (34.4%, 25.0 to 45.3), and those living in areas with the highest COVID-19 morbidity (29.9%, 21.2 to 39.8). The largest increases by diagnostic groups were found for eating disorders (27.4%, 8.0 to 55.3), depression and anxiety (21.0%, 12.1 to 51.9), and neurodevelopmental disorders (9.6%, 3.0 to 17.0), but psychotic and bipolar disorders and conduct and oppositional disorders showed no significant differences and self-harm (-28.6, -41.5 to -8.2) and substance use disorders (-15.5, -26.4 to -0.7) decreased in this period. The main limitation is that data from specialist services do not allow to draw conclusions about those not seeking help.

CONCLUSIONS

Following the first pandemic phase, new psychiatric diagnoses in children and adolescents increased by nearly a fifth in Finnish specialist services. Possible explanations to our findings include changes in help-seeking, referrals and psychiatric problems, and delayed service access.

Labor epidural analgesia and subsequent risk of offspring autism spectrum disorder and attention-deficit/hyperactivity disorder: a cross-national cohort study of 4.5 million individuals and their siblings

BACKGROUND

A recent study has suggested that labor epidural analgesia may be associated with increased rates of offspring autism spectrum disorder. Subsequent replication attempts have lacked sufficient power to confidently exclude the possibility of a small effect, and the causal nature of this association remains unknown.

OBJECTIVE

This study aimed to investigate the extent to which exposure to labor epidural analgesia is associated with offspring autism spectrum disorder and attention-deficit/hyperactivity disorder following adjustments for unmeasured familial confounding.

STUDY DESIGN

We identified 4,498,462 singletons and their parents using the Medical Birth Registers in Finland (cohorts born from 1987-2005), Norway (1999-2015), and Sweden (1987-2011) linked with population and patient registries. These cohorts were followed from birth until they either had the outcomes of interest, emigrated, died, or reached the end of the follow-up (at mean ages 13.6-16.8 years), whichever occurred first. Cox regression models were used to estimate country-specific associations between labor epidural analgesia recorded at birth and outcomes (eg, at least 1 secondary care diagnosis of autism spectrum disorder and attention-deficit/hyperactivity disorder or at least 1 dispensed prescription of medication used for the treatment of attention-deficit/hyperactivity disorder). The models were adjusted for sex, birth year, birth order, and unmeasured familial confounders via sibling comparisons. Pooled estimates across all the 3 countries were estimated using inverse variance weighted fixed-effects meta-analysis models.

RESULTS

A total of 4,498,462 individuals (48.7% female) were included, 1,091,846 (24.3%) of which were exposed to labor epidural analgesia. Of these, 1.2% were diagnosed with autism spectrum disorder and 4.0% with attention-deficit/hyperactivity disorder. On the population level, pooled estimates showed that labor epidural analgesia was associated with increased risk of offspring autism spectrum disorder (adjusted hazard ratio, 1.12; 95% confidence interval, 1.10-1.14, absolute risks, 1.20% vs 1.07%) and attention-deficit/hyperactivity disorder (adjusted hazard ratio, 1.20; 95% confidence interval, 1.19-1.21; absolute risks, 3.95% vs 3.32%). However, when comparing full siblings who were differentially exposed to labor epidural analgesia, the associations were fully attenuated for both conditions with narrow confidence intervals (adjusted hazard ratio [autism spectrum disorder], 0.98; 95% confidence interval, 0.93-1.03; adjusted hazard ratio attention-deficit/hyperactivity disorder, 0.99; 95% confidence interval, 0.96-1.02).

CONCLUSION

In this large cross-national study, we found no support for the hypothesis that exposure to labor epidural analgesia causes either offspring autism spectrum disorder or attention-deficit/hyperactivity disorder.

Challenges and Neuropsychological Functioning in Children and Adolescents with Borderline Intellectual Functioning

This retrospective chart review study sought to explore neuropsychological profiles, neuropsychiatric and psychiatric comorbidity, changes in diagnoses, support at daycare and school, medication use, psychiatric referrals, and progression into further education in a cohort of participants with borderline intellectual functioning (BIF). Additionally, developmental factors connected to BIF were studied. Delays in language and gross motor development were the initial reasons for the parents to seek health care. Comorbid neuropsychiatric and psychiatric diagnoses were frequent, a total of 41% of participants were referred to psychiatric services, and 45% used medication. Educational support was needed by 92% of the study participants. The majority of those graduating elementary school continued their studies at ordinary or special vocational schools. The risk of dropping out during secondary studies appeared to increase. The results in most of the neuropsychological subdomains declined over time, and 23% of the participants were later diagnosed with an intellectual disability (ID). The early developmental signs pointing towards BIF and the need for prompt support were a delay in language and motor development, difficulties in executive function, a delay in learning the activities of daily living among children under school age, and difficulties in reading and arithmetic skills and abstract reasoning at school age. It is important to follow up and support individuals with BIF as their risk for being left behind in the society is increased. Also, it would be important to repeat the neuropsychological testing of cognitive and adaptive functions before graduating elementary school as to capture those who meet the ID criteria.

The association between treated psychiatric and neurodevelopmental disorders and out-of-home care among Finnish children born in 1997

Comprehensive overviews of the use of psychiatric services among children and adolescents placed in out-of-home care (OHC) by child welfare authorities are scarce. We examine specialized service use for psychiatric and neurodevelopmental disorders among children and adolescents in a total population involving children in OHC. We used the longitudinal administrative data of a complete Finnish birth cohort 1997 (N = 57,174). We estimated risk ratios (RRs) for a range of diagnosed psychiatric and neurodevelopmental disorders among children in OHC. We also estimated RRs for OHC among those with diagnosed disorders. We used descriptive methods to explore the timing of first entry into OHC relative to the first diagnosis. Among children in OHC, 61.9% were diagnosed with any psychiatric or neurodevelopmental disorder, compared with 18.0% among those never in OHC (RR: 3.7; 95% CI 3.6-3.8). The most common diagnosed disorders among children in OHC were depression and anxiety disorders, neurodevelopmental disorders, and oppositional defiant disorder/conduct disorder (ODD/CD). Among all children with any diagnosis, 18.1% experienced OHC, compared with 2.5% among those without a diagnosis (RR: 7.4; 95% CI 6.9-7.9). Of those diagnosed with self-harm and suicidality, ODD/CD, substance-related disorders, and psychotic and bipolar disorders, 43.5-61.2% experienced OHC. Of the children in OHC receiving psychiatric services, half were diagnosed before first placement in OHC. The majority of children with experience in OHC were diagnosed with psychiatric or neurodevelopmental disorders. They comprised a significant proportion of individuals treated for severe and complex psychiatric disorders and self-harm.

Potential for prediction of psychosis and bipolar disorder in Child and Adolescent Mental Health Services: a longitudinal register study of all people born in Finland in 1987

Current strategies to predict psychosis identify only a small proportion of individuals at risk. Additional strategies are needed to increase capacity for pre-diction and prevention of serious mental illness, ideally during childhood and adolescence. One possible approach would be to investigate systems in which psychosis risk factors are concentrated during childhood. One notable such system is represented by Child and Adolescent Mental Health Services (CAMHS). Although psychotic disorders are uncommon in CAMHS, many risk factors for psychosis are highly prevalent in young people who enter this system. We hypothesized, therefore, that youth attending CAMHS would be a high-risk group for psychosis if followed into adulthood and, furthermore, that CAMHS systems would capture a substantial proportion of future psychosis cases. We constructed a total population cohort study of all Finns born in 1987 (N=55,875), linking together extensive register data on health care contacts from birth through age 28 years. We identified all individuals diagnosed with a psychotic or bipolar disorder by age 28 (N=1,785). The risk of psychosis/bipolar disorder by age 28 years was 1.8% for individuals who had not attended CAMHS during childhood or adolescence, whereas it was 12.8% for those with a history of any outpatient CAMHS contact (odds ratio, OR=7.9, 95% CI: 7.2-8.7). Furthermore, the risk of psychosis/bipolar disorder by age 28 years was 2.3% for individuals without a history of inpatient CAMHS admission, whereas it was 24.0% for those with a history of inpatient CAMHS admission (OR=13.3, 95% CI: 11.9-14.9), and 36.5% for those with a history of inpatient CAMHS admission in adolescence (age 13-17 years) (OR=24.2, 95% CI: 21.2-27.6). Individuals who attended CAMHS but received no mental disorder diagnosis had an equally high risk of subsequently developing a psychosis/bipolar disorder as individuals who did receive a diagnosis (OR=0.9, 99.5% CI: 0.7-1.1). Compared to other CAMHS attendees, individuals who developed psychosis or bipolar disorder were more likely to have had an initial CAMHS diagnosis of depressive or other mood disorder (OR=2.3, 99.5% CI: 1.6-3.0) and disruptive behaviour disorder (OR=1.7, 99.5% CI: 1.2-2.5). Of all psychosis/bipolar diagnoses by age 28 years, 50.2% occurred in individuals who had, at some point in childhood or adolescence, attended CAMHS, indicating that CAMHS represent not only a high-risk but also a high-capacity system for prediction of psychosis/bipolar disorder. These findings suggest an enormous, untapped potential for large-scale psychosis/bipolar disorder prediction and prevention research within existing specialist CAMHS.

Maternal serum persistent organic pollutant exposure and offspring diagnosed ADHD in a national birth cohort

BACKGROUND

Evidence implicates environmental factors in attention-deficit/hyperactivity disorder (ADHD) risk. Prenatal exposures to polychlorinated biphenyls (PCBs) and the pesticide metabolite p,p'-dichlorodiphenyl dichloroethylene (DDE) have been linked to lower cognitive ability, increased impulsivity, and attention related deficits in the offspring. However, information on the relationship of these exposures to the risk of clinically diagnosed ADHD is limited.

OBJECTIVES

To determine whether prenatal maternal levels of PCBs or DDE are associated with ADHD diagnosis in the offspring.

METHODS

The investigation was conducted in the Finnish Prenatal Study of ADHD (FIPS-ADHD), a case-control study nested in a national birth cohort. Cases were born in 1998 or 1999 and diagnosed with ADHD (ICD-9 314x or ICD-10 F90. x) according to the national Care Register for Health Care. Each case was individually matched to a control on sex, date, and place of birth. PCB congeners (PCB 74, 99, 118, 138, 153, 156, 170, 180, 183, 187) and DDE were quantified from archived prenatal maternal sera from 359 matched case-control pairs using gas chromatography - high triple quadrupole mass spectrometry. Maternal total PCBs were quantified as the sum of concentrations of the measured congeners. Associations with ADHD were examined using conditional logistic regression.

RESULTS

Maternal PCB or DDE levels greater than the 75th percentiles of the control distributions showed no evidence of association with offspring ADHD (PCBs: adjusted odds ratio (aOR) = 1.01, 95% CI = 0.63, 1.60), p = 0.98; DDE: aOR = 1.13, 95% CI = 0.71, 1.81; p = 0.60). Maternal levels of either pollutant dichotomized at the 90th percentile or considered as a continuous variable also did not show evidence for association with offspring ADHD diagnosis.

DISCUSSION

This study did not find evidence for association of maternal prenatal levels of PCBs or DDE with clinical diagnosis of offspring ADHD; however, this does not rule out the possibility of an impact on subclinical phenotypes.

Positive maternal mental health during pregnancy and mental and behavioral disorders in children: A prospective pregnancy cohort study

BACKGROUND

The role of positive maternal mental health during pregnancy in child mental health remains largely unknown. We investigated whether positive maternal mental health during pregnancy is associated with lower hazards of mental and behavioral disorders in children and mitigates the adverse effects of negative maternal mental health.

METHODS

Among 3,378 mother-child dyads of the Prediction and Prevention of Preeclampsia and Intrauterine Growth Restriction study, mothers reported their positive mental health biweekly throughout pregnancy with the Positive and Negative Affect Schedule, the Spielberger State Anxiety Inventory Curiosity scale, and a visual analogue scale for social support, and negative mental health with the Center for Epidemiologic Studies Depression Scale. We extracted data on their mental and behavioral disorder diagnoses from a nationwide medical register. This register provided data on their children's mental and behavioral disorder diagnoses as well, from birth until 8.4-12.8 (Median = 10.2, Interquartile Range 9.7-10.8) years of age.

RESULTS

A positive maternal mental health composite score during pregnancy was associated with a lower hazard of any mental and behavioral disorder among all children [Hazard Ratio (HR) = 0.79, 95% Confidence Interval (CI) 0.71 - 0.87] and among children of mothers experiencing clinically relevant depressive symptoms during pregnancy [HR = 0.80, 95%CI 0.64 - 1.00] and/or mental and behavioral disorders before or during pregnancy [HR = 0.69, 95%CI 0.55-0.86]. These associations were independent of covariates.

CONCLUSIONS

Children whose mothers had more positive mental health during pregnancy were less likely to develop mental and behavioral disorders. Protective effects were seen also among children of mothers facing mental health adversities before or during pregnancy.

Morbidities and mortality of diagnosed attention deficit hyperactivity disorder (ADHD) over the youth lifespan: A population-based retrospective cohort study

OBJECTIVES

To estimate the prevalence of ADHD, and related comorbidities, mortality, and type of health service use among children and young adults, using different case definitions.

METHODS

We conducted a population-based retrospective cohort study between 2000 and 2018, using the Quebec Integrated Chronic Disease Surveillance System (QICDSS) database. All residents aged less than 25 years eligible for health insurance coverage were included. We compared outcomes of three indicators (morbidity, services use and mortality) according two different algorithms of ADHD definitions, to the general population.

RESULTS

The cumulative prevalence of ADHD has risen steadily over the past decade, reaching 12.6% in 2017-2018. People with ADHD have a higher prevalence of psychiatric comorbidities, make greater use of medical, mental health services, and are hospitalized more often. The comparison of prevalence between the two algorithms and the general population for the three indicators showed that the cohort having one claim was very close to that with two or more, and statistically significant higher to that of people without ADHD.

CONCLUSION

This finding support that a single claim algorithm for ADHD can be used for case definition. More research is needed on the impact of potentially effective treatments in improving consequences of ADHD.

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.

Risk for Premature Mortality and Intentional Self-harm in Autism Spectrum Disorders

To examine the risk for premature mortality and intentional self-harm in autism spectrum disorders (ASD). Based on a national birth cohort. Children born in 1987-2005, diagnosed with ASD by 2007 (n = 4695) were matched with four non-ASD subjects (n = 18,450) and followed until 2015 for mortality and intentional self-harm. The risk among ASD subjects was elevated only for natural cause of death. The risk for intentional self-harm was increased in the unadjusted analyses, but decreased to non-significant after adjusting for comorbid psychiatric disorders. ASD subjects are at increased risk for premature mortality due to natural causes of death. While ASD subjects die of suicide and present with more self-harm, the association is explained by comorbid psychiatric disorders.

Increased Risk of ADHD at Short and Long Interpregnancy Intervals in a National Birth Cohort

BACKGROUND

Short or long interpregnancy interval (IPI) may adversely impact conditions for foetal development. Whether attention deficit hyperactivity disorder (ADHD) is related to IPI has been largely unexplored.

OBJECTIVES

To examine the association between IPI and ADHD in a large, population-based Finnish study.

METHODS

All children born in Finland between 1991 and 2005 and diagnosed with ADHD (ICD-9 314x or ICD-10 F90.x) from 1995 to 2011 were identified using data from linked national registers. Each subject with ADHD was matched to 4 controls based on sex, date of birth, and place of birth. A total of 9564 subjects with ADHD and 34,479 matched controls were included in analyses. IPI was calculated as the time interval between sibling birth dates minus the gestational age of the second sibling. The association between IPI and ADHD was determined using conditional logistic regression and adjusted for potential confounders.

RESULTS

Relative to births with an IPI of 24 to 59 months, those with the shortest IPI (<6 months) had an increased risk of ADHD (odds ratio [OR] 1.30, 95% confidence interval (CI) 1.12, 1.51) and the ORs for the longer IPI births (60-119 months and ≥120 months) were 1.12 (95% CI 1.02, 1.24) and 1.25 (95% CI 1.08, 1.45), respectively. The association of longer IPI with ADHD was attenuated by adjustment for maternal age at the preceding birth, and comorbid autism spectrum disorders did not explain the associations with ADHD.

CONCLUSIONS

The risk of ADHD is higher among children born following short or long IPIs although further studies are needed to explain this association.

Relative age and specific learning disorder diagnoses: A Finnish population-based cohort study

Background

Being among the youngest in class has previously been associated with attention-deficit/hyperactivity disorder (ADHD) and academic disadvantage, but the relative age effect on learning disorders is less well understood. This study examined whether relatively young children are more likely to be diagnosed with specific learning disorders than their older peers.

Methods

The setting included all 388,650 children born singleton in Finland from 1996 to 2002. Cases diagnosed with specific learning disorders in specialized health care by the age of 10 were identified from national registers. Cumulative incidences of specific learning disorders and the corresponding incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were calculated for each birth month compared to January.

Results

During follow-up, 3162 (0.8% of 388,650) children were diagnosed with a specific learning disorder. Children born in December displayed higher cumulative incidences for specific learning disorders than children born in January (IRR: 1.77, 95% CI: 1.50-2.11). The findings were similar for girls (IRR: 2.01, 1.44-2.83) and boys (IRR: 1.70, 1.39-2.08). ADHD did not explain the association, as the IRR for the youngest children with specific learning disorders and ADHD was 1.59 (1.13-2.26) compared to those without ADHD (IRR: 1.84, 1.51-2.24).

Conclusions

Relatively younger children in Finnish schools were more likely to be diagnosed with a specific learning disorder by the age of 10. Increased awareness of how relative age differences affect the likelihood for children to be diagnosed with specific learning disorders is needed among parents, clinicians, and teachers.

Restless sleep disorder in children with attention-deficit/hyperactivity disorder

STUDY OBJECTIVES

Restless sleep is a very common parental complaint in children with attention-deficit/hyperactivity disorder (ADHD), but restless sleep has been seen in association with other comorbidities such as restless legs syndrome and obstructive sleep apnea. Restless sleep disorder (RSD) needs to be identified from other disorders when evaluating children with ADHD. In this study we aim to identify the prevalence of RSD in children with ADHD referred to our sleep center.

METHODS

This is a retrospective study of children with ADHD who underwent polysomnography. The following diagnostic and descriptive data were obtained for each patient: age, sex, presence/absence of RSD, other sleep disorders, psychiatric comorbidities, and medications. RSD was diagnosed per diagnostic criteria.

RESULTS

There were 66 children with ADHD. All of them underwent polysomnography, 17 were females, and 49 were males. Mean age was 11.6 years (± 3.6 standard deviation). The complaint of restless sleep was reported by the parents of 54 (81.1%) of the children; however, only 6 of them (9.1%) were diagnosed with RSD. Seventy-one percent had obstructive sleep apnea and 19.7% had restless legs syndrome. A significant number of patients had psychiatric comorbidities and were on various medications.

CONCLUSIONS

Although restless sleep is a common complaint reported in 81.1% of children with ADHD, only 9.1% had RSD. Most causes of restless sleep are secondary and associated with other sleep disorders, psychiatric comorbidities, or medication use.

Maternal Vitamin D Levels and the Risk of Offspring Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Recent evidence has highlighted the importance of vitamin D in the development of the central nervous system. Some studies have shown an association between maternal vitamin D deficiency during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD) symptoms based on parent or teacher ratings. There are no previous studies on early pregnancy 25-hydroxyvitamin D [25(OH)D] levels and the risk of diagnosed offspring ADHD. Our aim was to examine maternal 25(OH)D levels in early pregnancy and offspring ADHD.

METHOD

In this nationwide population-based case-control study, 1,067 ADHD cases (born between 1998 and 1999 and diagnosed according to the International Classification of Diseases) and 1,067 matched controls were identified from Finnish registers. Maternal 25(OH)D levels were measured using quantitative immunoassay from maternal sera, collected during the first trimester and archived in the national biobank. Conditional logistic regression was used to examine the association between maternal 25(OH)D and offspring ADHD.

RESULTS

There was a significant association between decreasing log-transformed maternal 25(OH)D levels and offspring ADHD both in the unadjusted analyses (odds ratio 1.65; 95% CI 1.33-2.05; p < .001) and in the analyses adjusting for maternal socioeconomic status and age (odds ratio 1.45; 95% CI 1.15-1.81; p = .002). Analyses by quintiles of maternal 25(OH)D levels in the lowest versus highest quintile revealed an adjusted odds ratio for offspring ADHD of 1.53 (95% CI 1.11-2.12; p = .010).

CONCLUSION

This study demonstrated an association between low maternal 25(OH)D during pregnancy and an elevated risk for offspring ADHD. If replicated in independent samples, this finding may have significant public health implications.

Maternal serum Vitamin B12 and offspring attention-deficit/hyperactivity disorder (ADHD)

Maternal Vitamin B12 deficiency during pregnancy is associated with offspring neuropsychiatric disorders. Few previous studies examining this association with attention-deficit/hyperactivity disorder (ADHD) report inconsistent findings. The study examines the association between maternal serum Vitamin B12 levels and offsprings' risk of ADHD. This study is based on the Finnish Prenatal Study of ADHD with a nested case-control design. All the singleton children born in Finland between January 1998 and December 1999 and diagnosed with ADHD were included in the study. A total of 1026 cases were matched with an equal number of controls on sex, date of birth and place of birth. Maternal Vitamin B12 levels were assessed using a chemiluminescence microparticle immunoassay and archived from maternal serum banks, collected during the first and early second trimester of pregnancy. Lower maternal Vitamin B12 levels when analyzed as a continuous variable was not associated with offspring ADHD (aOR 0.97, 95% CI 0.79-1.18, p = 0.75). No significant associations were seen in the lowest quintile of Vitamin B12 levels (aOR 0.96, 95% CI 0.73-1.27, p = 0.80). This is the first study examining maternal sera Vitamin B12 levels during early pregnancy and offspring ADHD. The result suggests that Vitamin B12 deficiency during early pregnancy has specificity for some disorders but not with offspring ADHD.

The effects of sex on prevalence and mechanisms underlying neurodevelopmental disorders

Neurodevelopmental disorders occur more frequently in boys than in girls and often differ in presentation between the sexes. The sex differences in prevalence and presentation of autism spectrum disorder, intellectual disability, communication disorders, specific learning disabilities, attention deficit/hyperactivity disorder, Tourette's syndrome, and epilepsy are discussed, as well as sex differences in the patterns of comorbidities between these disorders. Prominent theories have been proposed to explain sex biases. These include genetic factors, sex hormones, sociological factors, cognitive differences between the sexes, and environmental insult. Despite the large body of research reviewed in this chapter, many aspects of sex-related effects in neurodevelopmental disorders remain poorly understood.

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.

The impact of parental psychopathology and sociodemographic factors in selective mutism - a nationwide population-based study

BACKGROUND

Selective mutism (SM) is nowadays considered a relatively rare anxiety disorder characterized by children failing to speak in certain situations. Research on risk factors for SM are limited in comparison to other psychiatric disorders. The aim of this study was to examine several potential risk factors for SM in a large nationwide cohort, namely parental psychopathology, parental age, maternal SES, urbanicity, maternal marital status and parental immigration status.

METHODS

This nested case-control study comprised 860 cases with SM, identified from the Finnish Hospital Discharge Register and 3250 controls matched for sex and age from the Finnish Central Population Register. Conditional logistic regression was used to examine the association between the risk factors and SM.

RESULTS

If both parents had any psychiatric disorder, this almost tripled their odds of having a child with SM (OR 2.8, 95% CI 2.0-4.0). There were increased rates of all types of psychiatric disorders in the parents of the children with SM, with a wider range of diagnoses among the mothers than fathers. Fathers over 35 years (OR 1.4, 95% CI 1.1-1.8) were significantly more likely to have children with SM. Offspring of a single mother had a 2-fold (OR = 2.0, 95% CI 1.4-3.0) increased odds of SM than mothers who were married or in a relationship.

CONCLUSIONS

Several parental psychiatric disorders were associated with offspring SM. This points towards a shared aetiology of psychiatric disorders. Findings on paternal age and single motherhood help to improve our understanding of risk factors for SM.

Attention Deficit Hyperactivity Disorder and Psychiatric Comorbidities

Aim: This study aims to obtain current information on the clinical features of attention deficit hyperactivity disorder cases, comorbid psychiatric disorders and psychiatric drug use. Methods: All patients between the ages of 6 and 18 years who were admitted to our outpatient clinic and diagnosed with attention deficit hyperactivity disorder were included in the study. The files of the patients were examined and their demographic characteristics, symptoms, psychiatric diagnoses and drug profiles were recorded. The pattern of the psychiatric disorders accompanied by attention deficit hyperactivity disorder cases and the differences according to age and gender were analyzed. The differences were determined in patients with psychiatric comorbidity compared to those without. Result: The mean age of the 777 patients included in the study was 11.1±2.94 and 76.6% were boys. 60.9% of attention deficit hyperactivity disorder patients had comorbid psychiatric disorders. The most common psychiatric comorbidities were specific learning disability (23.6%), oppositional defiant disorder (12.9%) and conduct disorder (12.1%). There was no difference between the genders in terms of the incidence of psychiatric comorbidities. The rate of psychiatric comorbidity was significantly higher in adolescents than in children. A psychotropic medication was used in 86.4% of the cases and psychotropic polypharmacy was present in 31.5%. The rate of polypharmacy was significantly higher in the group with psychiatric comorbidity. Conclusion: Attention deficit hyperactivity disorder is frequently accompanied by other psychiatric disorders and the psychiatric comorbidity leads to a more complicated clinical profile. Approximately one-third of attention deficit hyperactivity disorder patients have psychiatric polypharmacy and these patients should be carefully monitored. Primary care physicians who are frequently confronted with attention deficit hyperactivity disorder cases should be careful about psychiatric comorbidities. Keywords: Child psychiatry, attention deficit hyperactivity disorder, mental disorders, Family practice

Gender- and age-stratified analyses of ADHD medication use in children and adolescents in Finland using population-based longitudinal data, 2008-2018

Aims: This study examined medication use for attention-deficit/hyperactivity disorder (ADHD) among children and adolescents by gender in Finland during 2008-2018. Methods: Aggregated data on medication use for ADHD from 2008 to 2018 were extracted from the nationwide register on reimbursed prescriptions. The annual prevalence of ADHD medication use was calculated as the number of children (6-12 years) and adolescents (13-17 years) per calendar year with at least one ADHD medication purchase divided by the number of children and adolescents in the population. Population prevalence for children was also examined by birth month. Results: In 2008, the prevalence rates for males were 1.26% in children and 0.93% in adolescents, and for females 0.21% and 0.14%, respectively. In 2018, the prevalence rates for males were 4.42% in children and 4.21% in adolescents, and for females 0.99% and 1.28%, respectively. Male-to-female ratios decreased during the study period from 6.0:1 to 4.5:1 (children) and from 6.6:1 to 3.3:1 (adolescents). ADHD medication use was more common among males and females (aged 6-12 years) born in May-August or September-December than among males and females born in January-April. Conclusions: The prevalence of ADHD medication use has continued to increase in Finland. Although use has increased more rapidly among females resulting in lower male-to-female ratios, medication use among females is considerably lower compared with males. Consequently, gender discrepancy in 2018 was relatively large, particularly among children. Future studies should also consider reporting annual prevalence by children's birth month.

Maternal serum C-reactive protein (CRP) and offspring attention deficit hyperactivity disorder (ADHD)

Exposure to infection and inflammation during the fetal period are associated with offspring neuropsychiatric disorders. Few previous studies have examined this association with ADHD with mixed findings. This study aims to examine the association between early gestational maternal C-reactive protein (CRP), prospectively assayed in stored maternal sera and the risk of ADHD in offspring. This study is based on the Finnish Prenatal studies of ADHD (FIPS-ADHD) with a nested case-control design. It includes all singleton-born children in Finland between January 1, 1998 and December 31, 1999 and diagnosed with ADHD. A total of 1079 cases and equal number of controls were matched on date of birth, sex and place of birth. Maternal CRP levels were assessed using a latex immunoassay from archived maternal serum specimens, collected during the first and early second trimester of pregnancy. Elevated maternal CRP when analyzed as a continuous variable was not associated with offspring ADHD (OR 1.05, 95% CI 0.96-1.15). No significant associations were seen in the highest quintile of CRP (OR 1.18, 95% CI 0.88-1.58). The results were similar in both sexes as well as among ADHD cases with or without comorbid ASD or conduct disorder. In this first study examining CRP, a biomarker for inflammation, during early pregnancy in relation to offspring ADHD, we report no significant associations. The lack of any association, when considered with positive findings seen in ASD and schizophrenia, and negative findings in bipolar disorder suggests different pathways linking maternal immune activation and development of various neuropsychiatric disorders.

Psychiatric Comorbidity and Demographic Characteristics of 1,000 Children and Adolescents With ADHD in Turkey

Objective: The objective was to examine the frequency of comorbid disorders in children and adolescents with ADHD in Turkey and to evaluate the distribution of comorbidities according to the subtypes of ADHD and sociodemographic features. Method: The sample consisted of 1,000 children, 6 to 18 years of age, including 242 females and 758 males, from Ege University who were diagnosed with ADHD. Results: The overall prevalence rate of psychiatric comorbidity in the study was 56.3%. The most frequently observed comorbidity was oppositional defiant disorder with a rate of 37.4%. Conduct disorder, depressive disorder, obsessive-compulsive disorder, and anxiety disorder accompanied ADHD, respectively. The results revealed that 70.2% of the children with ADHD-Combine type had at least one psychiatric comorbidity. Oppositional defiant disorder, conduct disorder, depressive disorder, and obsessive-compulsive disorder accompanied ADHD-Combine type in 54.6%, 12.6%, 8.1%, and 8.8% of the participants, respectively. Conclusion: These findings provide valuable information about the comorbid disorders in children and adolescents with a very large clinical sample of ADHD children.

Parental immigration and offspring post-traumatic stress disorder: A nationwide population-based register study

OBJECTIVES

The aim of this study was to investigate the association between parental immigration status and a diagnosis of post-traumatic stress disorder (PTSD) in their offspring.

METHODS

This nested matched case-control study was based on a Finnish national birth cohort for 1987-2010 and cases were diagnosed with PTSD by 2012 from the Care Register for Health Care. We identified 3639 cases and 14,434 controls individually matched for gender, place and date of birth (±30 days). Conditional logistic regression analyses were conducted to examine the association between parental immigration status, parents' region of birth and time since paternal immigration, and PTSD after controlling for confounding factors.

RESULTS

The likelihood of being diagnosed with PTSD was significantly increased among children with an immigrant father (OR 1.8, 95% CI 1.3 - 2.4) than those with two Finnish parents and one immigrant mother. There was no significant association between having an immigrant mother or two immigrant parents and receiving a diagnosis of PTSD. The likelihood of being diagnosed with PTSD was increased if the children's fathers had migrated less than five years before their birth (OR 1.4, 95% CI 1.03 - 1.9) and if their immigrant fathers had been born in North Africa or the Middle East (OR 2.1, 95% CI 1.4 - 3.3).

LIMITATIONS

The sample included a heterogeneous migrant group without information on the reason for migration. The cases were identified from hospital diagnosis that may have only included severe cases.

CONCLUSION

The increased likelihood of a diagnosis of PTSD underlines the need for psychosocial services among second-generation immigrants.

Changes in mental health service use among 8-year-old children: a 24-year time-trend study

The use of children's mental health services has increased, but most children with psychiatric problems are still not in contact with these services. This time-trend study assessed changes in considered and reported service use over a 24-year period and studied the factors associated with it using four cross-sectional studies. Information was gathered on 8-year-old children living in the area covered by Turku University Hospital, Finland, at four time points: 986 children in 1989, 891 in 1999, 930 in 2005, and 942 in 2013. The same study design, methods and school districts were used each year and the participation rates varied between 86 and 95%. Parents and teachers completed questionnaires concerning the child's psychiatric symptoms and service use. The considered and reported service use increased continuously during the study period. In 1989, 2.4% of children had used services and in 2013 this was 11.0% (OR 5.0, 95% CI 3.1-8.0). Reported service use also increased among children with comorbid problems, from 18.3 to 50.7% (OR 5.0, 95% CI 2.1-12.0). Psychiatric problems and some family factors were associated with service use, but the increase was not explained by these factors. The increase in child mental health service use may reflect better public awareness of mental health problems, fewer barriers to accessing care and decrease of stigma. Although more children are using mental health services, there are still a large number of children with mental health problems who have not been in contact with services.

Prenatal Cotinine Levels and ADHD Among Offspring

OBJECTIVES

An association between maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD) has been shown across several studies based on self-reports. No previous studies have investigated the association of nicotine exposure measured by cotinine levels during pregnancy and offspring ADHD.

METHODS

In this population-based study, 1079 patients born between 1998 and 1999 and diagnosed with ADHD according to the International Classification of Diseases and 1079 matched controls were identified from Finnish nationwide registers. Maternal cotinine levels were measured by using quantitative immunoassays from maternal serum specimens collected during the first and second trimesters of pregnancy and archived in the national biobank.

RESULTS

There was a significant association between increasing log-transformed maternal cotinine levels and offspring ADHD. The odds ratio was 1.09 (95% confidence interval [CI] 1.06-1.12) when adjusting for maternal socioeconomic status, maternal age, maternal psychopathology, paternal age, paternal psychopathology, and child's birth weight for gestational age. In the categorical analyses with cotinine levels in 3 groups, heavy nicotine exposure (cotinine level >50 ng/mL) was associated with offspring ADHD, with an odds ratio of 2.21 (95% CI 1.63-2.99) in the adjusted analyses. Analyses by deciles of cotinine levels revealed that the adjusted odds for offspring ADHD in the highest decile was 3.34 (95% CI 2.02-5.52).

CONCLUSIONS

The study reveals an association with and a dose-response relationship between nicotine exposure during pregnancy and offspring ADHD. Future studies incorporating maternal smoking and environmental, genetic, and epigenetic factors are warranted.

Attention-deficit/hyperactivity disorder and risk for psychiatric and neurodevelopmental disorders in siblings

BACKGROUND

Probands with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for several psychiatric and neurodevelopmental disorders. The risk of these disorders among the siblings of probands has not been thoroughly assessed in a population-based cohort.

METHODS

Every child born in Finland in 1991-2005 and diagnosed with ADHD in 1995-2011 were identified from national registers. Each case was matched with four controls on sex, place, and date of birth. The full siblings of the cases and controls were born in 1981-2007 and diagnosed in 1981-2013. In total, 7369 cases with 12 565 siblings and 23 181 controls with 42 753 siblings were included in the analyses conducted using generalized estimating equations.

RESULTS

44.2% of the cases and 22.2% of the controls had at least one sibling diagnosed with any psychiatric or neurodevelopmental disorder (risk ratio, RR = 2.1; 95% CI 2.0-2.2). The strongest associations were demonstrated for childhood-onset disorders including ADHD (RR = 5.7; 95% CI 5.1-6.3), conduct and oppositional disorders (RR = 4.0; 95% CI 3.5-4.5), autism spectrum disorders (RR = 3.9; 95% CI 3.3-4.6), other emotional and social interaction disorders (RR = 2.7; 95% CI 2.4-3.1), learning and coordination disorders (RR = 2.6; 95% CI 2.4-2.8), and intellectual disability (RR = 2.4; 95% CI 2.0-2.8). Also, bipolar disorder, unipolar mood disorders, schizophrenia spectrum disorders, other neurotic and personality disorders, substance abuse disorders, and anxiety disorders occurred at increased frequency among the siblings of cases.

CONCLUSIONS

The results offer potential utility for early identification of neurodevelopmental and psychiatric disorders in at-risk siblings of ADHD probands and also argue for more studies on common etiologies.

Parental Risk Factors among Children with Reactive Attachment Disorder Referred to Specialized Services: A Nationwide Population-Based Study

This nationwide population-based register study examined the family and parental risk factors associated with offspring reactive attachment disorder (RAD). We identified 614 children diagnosed with RAD from the Finnish Care Register for Health Care and each case was matched with four controls. Univariate and multivariate models examined the associations between risk factors and RAD. In the multivariate model, offspring RAD was associated with only mother, only father and both parents having psychiatric diagnoses. Increased odds were observed for maternal smoking during pregnancy, single motherhood and paternal age ≥ 45 years. This study provides information on several parental adversities and offspring RAD that have important implications for public health, when planning early prevention and interventions in infant mental health.

Lower Apgar scores and Caesarean sections are related to attention-deficit/hyperactivity disorder

AIM

We examined the associations between prenatal, birth-related and newborn risk factors and attention-deficit/hyperactivity disorder (ADHD).

METHODS

In this population-based study, 10 409 subjects diagnosed with ADHD by 31 December 2011 and 39 124 controls, born between 1 January 1991 and 31 December 2005, were identified from Finnish nationwide registers. Perinatal data were obtained from the Birth Register. Conditional logistic regression was used to examine the associations after controlling for confounders.

RESULTS

Lower Apgar scores were associated with a higher risk of ADHD, with odds ratios of 1.12 (95% confidence intervals 1.06-1.19) for one-minute Apgar scores of 7-8, 1.17 (95% CI 1.02-1.35) for scores of 5-6 and 1.41 (95% CI 1.18-1.68) for scores of 0-4, compared to Apgar scores of 9-10. Elective Caesarean sections were associated with an increased risk of ADHD with an adjusted odds ratio of 1.15 (95% CI 1.05-1.26). Other identified risk factors were breech presentation, induced labour and admission to a neonatal intensive care unit. Low umbilical artery pH did not increase the risk of ADHD.

CONCLUSION

Elective Caesareans and perinatal adversities leading to lower Apgar scores increased the risk of ADHD. Future research to identify the mechanisms behind these findings is warranted.

Social risk factors for speech, scholastic and coordination disorders: a nationwide register-based study

Background

Broadly defined learning and coordination disorders (LCDs) are common in the population and have previously been associated with familial social risk factors and male sex. However, comprehensive nationwide studies of these risk factors in LCD subgroups are lacking. Our objective was to assess different LCDs in relation to sex and maternal education, marital status and socioeconomic status based on occupation.

Methods

We conducted a nationwide register-based study. The following diagnoses were identified from the Finnish Hospital Discharge Register (FHDR) according to the ICD-10 (n = 28,192): speech disorders (F80), scholastic disorders (F81), motor and coordination disorders (F82) and mixed developmental disorder (F83). To study cumulative incidence and male: female ratios of service use of LCDs, we used a cohort design among all Finnish children born singleton 1996–2007 (n = 690,654); to study social risk factors, we used a nested case-control design with extensive register data on both cases and matched controls (n = 106,616).

Results

The cumulative incidence was 4.7% for any LCD by age 15 and the changes in cumulative incidence over time were minor. The male: female ratios were 2.2–3.0 across LCD subgroups. Learning and coordination disorders were more common in households with lower maternal education, socioeconomic status based on occupation and among children with single mothers at the time of birth; the odds ratios (OR) for any LCD were 1.2–1.9 across risk factors. The odds for LCD diagnosis increased linearly with the number of social risk factors, except for coordination disorder. The effect size of three risk factors was highest in the group with mixed or multiple LCDs; OR 3.76 (95% CI 3.31–4.28).

Conclusions

Multiple social risk factors increase the odds for multiple, more comprehensive learning difficulties. The findings have implications for service planning, as early identification and interventions of learning and coordination disorders might reduce related long-term social adversities.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-5650-z) contains supplementary material, which is available to authorized users.

Neurodevelopmental disorders: prevalence and comorbidity in children referred to mental health services

BACKGROUND

Accurate prevalence rates of the neurodevelopmental disorders (ND) and comorbid conditions in child and adolescent mental health services (CAMHS) are essential for treatment planning and organization of health care. However, valid and reliable prevalence estimates from Nordic CAMHS populations are scarce, and the published findings vary.

AIMS

To report prevalence rates of ND (attention-deficit hyperactivity disorder: ADHD, tic disorder: TD or autism spectrum disorder: ASD) and comorbid disorders by a validated diagnostic instrument in children referred to CAMHS outpatient clinics.

METHODS

Parents of 407 consecutively referred children aged 7-13 years were interviewed with the semistructured interview schedule for affective disorders and schizophrenia, present and lifetime version (Kiddie-SADS-PL) at time of admittance.

RESULTS

One or more ND was diagnosed in 226 children (55.5%; 69.9% boys): ADHD (44.5%; 68.5% boys); TD (17.7%; 77.8% boys) and ASD (6.1%; 76% boys). Among children with ND 70 (31.0%) had only one ND with no comorbid disorder, 49 (21.7%) had more than one ND (homotypic comorbidity) and 131 (58%) had a non-ND psychiatric disorder (heterotypic comorbidity). Anxiety disorders were the most frequently occurring heterotypic comorbidity in all three ND. Comorbid depressive disorder was associated with older age, and comorbid anxiety disorder with female gender.

CONCLUSION

In children referred to CAMHS, ND constitute the most frequently occurring group of disorders, with high rates of both homotypic and heterotypic comorbidity. This needs to be taken into consideration in health service planning and treatment delivery.

Parental age and attention-deficit/hyperactivity disorder (ADHD)

Background

Previous studies have suggested that young mothers more often have children with ADHD. We used sibling comparisons to examine the nature of this association and to investigate if this association is explained by early environment or genetic and socioeconomic factors.

Methods

A large population-based cohort including all singletons born in Denmark from 1 January 1991 through 31 December 2005 was followed from birth until 30 April 2011. Data were available for 94% ( N  = 943 785) of the population. Offspring ADHD was identified by an ICD-10 diagnosis of Hyperkinetic Disorder (HKD). We used sibling-matched Cox regression to control for genetic and socioeconomic factors.

Results

In the population cohort we found that children born by parents aged 20 years or younger had more than twice the risk of being diagnosed with ADHD compared with children with parents between 26 and 30 years of age. When comparing full siblings the associations were attenuated, but we found a trend of increased risk of ADHD with decreasing maternal age, which was not seen for paternal age.

Conclusions

Sibling comparisons suggested that the associations between both maternal and paternal age and ADHD are partly explained by common genetic and socioeconomic factors. The trend of increased risk of ADHD with decreasing maternal age, but not with paternal age, may be linked to pregnancy or early-life environmental factors. Even though only a smaller part of the association can be attributed to environmental factors, there is a public health interest to support young parents through their first years of parenthood.

Vitamin-mineral treatment improves aggression and emotional regulation in children with ADHD: a fully blinded, randomized, placebo-controlled trial

BACKGROUND

Evaluation of broad-spectrum micronutrient (vitamins and minerals) treatment for childhood ADHD has been limited to open-label studies that highlight beneficial effects across many aspects of psychological functioning.

METHOD

This is the first fully blinded randomized controlled trial of medication-free children (n = 93) with ADHD (7-12 years) assigned to either micronutrients (n = 47) or placebo (n = 46) in a 1:1 ratio, for 10 weeks. All children received standardized ADHD assessments. Data were collected from clinicians, parents, participants and teachers across a range of measures assessing ADHD symptoms, general functioning and impairment, mood, aggression and emotional regulation.

RESULTS

Intent-to-treat analyses showed significant between-group differences favouring micronutrient treatment on the Clinical Global Impression-Improvement (ES = 0.46), with 47% of those on micronutrients identified as 'much' to 'very much' improved versus 28% on placebo. No group differences were identified on clinician, parent and teacher ratings of overall ADHD symptoms (ES ranged 0.03-0.17). However, according to clinicians, 32% of those on micronutrients versus 9% of those on placebo showed a clinically meaningful improvement on inattentive (OR = 4.9; 95% CI: 1.5-16.3), but no group differences on improvement in hyperactive-impulsive symptoms (OR = 1.0; 95% CI: 0.4-2.5). Based on clinician, parent and teacher report, those on micronutrients showed greater improvements in emotional regulation, aggression and general functioning compared to placebo (ES ranged 0.35-0.66). There were two dropouts per group, no group differences in adverse events and no serious adverse events identified. Blinding was successful with guessing no better than chance.

CONCLUSIONS

Micronutrients improved overall function, reduced impairment and improved inattention, emotional regulation and aggression, but not hyperactive/impulsive symptoms, in this sample of children with ADHD. Although direct benefit for core ADHD symptoms was modest, with mixed findings across raters, the low rate of adverse effects and the benefits reported across multiple areas of functioning indicate micronutrients may be a favourable option for some children, particularly those with both ADHD and emotional dysregulation. Trial registered with the Australian New Zealand Clinical Trials Registry ACTRN12613000896774.

A cross-sectional study of the relationship between infant Thimerosal-containing hepatitis B vaccine exposure and attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is characterized by a marked pattern of inattention and/or hyperactivity-impulsivity that is inconsistent with developmental level and interferes with normal functioning in at least two settings. This study evaluated the hypothesis that infant Thimerosal-containing hepatitis B vaccine (T-HepB) exposure would increase the risk of an ADHD diagnosis. This cross-sectional study examined 4393 persons between 13 and 19 years of age from the combined 1999-2004 National Health and Nutritional Examination Survey (NHANES) by analyzing demographic, immunization, socioeconomic, and health-related variables using the SAS system. Three doses of T-HepB exposure in comparison to no exposure significantly increased the risk of an ADHD diagnosis using logistic regression (adjusted odds ratio=1.980), linear regression (adjusted beta-coefficient=0.04747), Spearman's rank (Rho=0.04807), and 2×2 contingency table (rate ratio=1.8353) statistical modeling even when considering other covariates such as gender, race, and socioeconomic status. Current health status outcomes selected on an a priori basis to not be biologically plausibly linked to T-HepB exposure showed no relationship with T-HepB. The observed study results are biologically plausible and supported by numerous previous epidemiological studies, but because the NHANES data is collected on a cross-sectional basis, it is not possible to ascribe a direct cause-effect relationship between exposure to T-HepB and an ADHD diagnosis. During the decade from 1991 to 2001 that infants were routinely exposed to T-HepB in the United States (US), an estimated 1.3-2.5 million children were diagnosed with ADHD with excess lifetime costs estimated at US $350-$660 billion as a consequence of T-HepB. Although Thimerosal use in the HepB in the US has been discontinued, Thimerosal remains in the HepB in developing countries. Routine vaccination is an important public health tool to prevent infectious diseases, but every effort should be made to eliminate Thimerosal exposure.

Temporal changes in the incidence of treated psychiatric and neurodevelopmental disorders during adolescence: an analysis of two national Finnish birth cohorts

BACKGROUND

Comprehensive overviews of the temporal changes in treated psychiatric and neurodevelopmental disorders during adolescence are scarce. We reviewed data from two national cohorts, 10 years apart, to establish the change in use of specialised services for psychiatric and neurodevelopmental diagnoses in Finland.

METHODS

We compared the nationwide register-based incidence of psychiatric and neurodevelopmental diagnoses between the 12th birthday and 18th birthday of adolescents born in Finland in 1987 and 1997. Adolescents who emigrated or died before their 12th birthday and those with missing covariate data were excluded, as were those who, when aged 11 years, had lived in a municipality belonging to a hospital district with obviously incomplete data reports during any follow-up years in our study. Our primary outcomes were time to incident specialised service use for any psychiatric or neurodevelopmental disorder and for 17 specific diagnostic classes. We also investigated whether adolescents who died by suicide had accessed specialised services before their deaths.

FINDINGS

The cumulative incidence of psychiatric or neurodevelopmental disorders increased from 9·8 in the 1987 cohort to 14·9 in the 1997 cohort (difference 5·2 percentage points [95% CI 4·8-5·5]) among girls, and from 6·2 in the 1987 cohort to 8·8 in the 1997 (2·6 percentage points [2·4-2·9]) among boys. The hazard ratio for the overall relative increase in neurodevelopment and psychiatric disorders in the 1997 cohort compared with the 1987 cohort was 1·6 (95% CI 1·5-1·8) among girls and 1·5 (1·4-1·6) among boys. Of the studied diagnostic classes, we noted significant (ie, p<0·001) relative increases for ten of 17 diagnoses among girls and 11 among boys. Of the adolescents who died by suicide before age 18, only five of 16 in the 1987 cohort and two of 12 in the 1997 cohort had used specialised services in the 6 months before their death.

INTERPRETATION

The large absolute rise in service use for psychiatric or neurodevelopmental disorders points to the need to deliver effective treatment to a rapidly increased patient population, whereas the relative increase in specific diagnoses should inform clinical practice. Despite increasing service use, identification of adolescents at risk of suicide remains a major public health priority.

FUNDING

Academy of Finland, Brain and Behavior Research Foundation, Finnish Medical Foundation.

A cross-sectional study of the relationship between blood lead levels and reported attention deficit disorder: an assessment of the economic impact on the United States

Attention deficit disorder (ADD) is characterized by a pattern of inattention and/or impulsivity that is inconsistent with developmental level and interferes with normal functioning in at least two settings. A recent meta-analysis suggested a significant relationship between lead (Pb) exposure and attention deficit symptoms. This study evaluated the potential relationship between increasing blood Pb levels and the risk of a reported ADD diagnosis. This cross-sectional study examined a sample of 2109 persons (32,762,158 weighted-persons) between 10 and 19 years-old from the 2003-2004 National Health and Nutritional Examination Survey (NHANES). This study analyzed demographic, socioeconomic, health related-questions, and laboratory tests using survey logistic and frequency modeling in SAS. On a microgram (μg)/deciliter (dL) basis, a significant dose-response relationship between increasing blood Pb levels and the risk of a reported ADD outcome was confirmed (odds ratio (OR) = 1.237, p = 0.0227). The relationship between increasing blood Pb levels and the risk of a reported ADD remained consistent when examining covariates such as gender, race, and socioeconomic status (OR = 1.292, p = 0.0301). Control outcomes selected on an a priori basis to not be biologically plausibly linked to blood Pb levels showed no relationship with increasing blood Pb levels. This NHANES analysis revealed an estimated 380,000 persons born in the United States (US) from 1984 to 1993 were reported to have an ADD outcome as a consequence of elevated blood Pb levels and the excess lifetime costs of these persons would be about US $100 billion. Every effort should be made to eliminate childhood Pb exposure.

The Prevalence of Internet Addiction Among a Japanese Adolescent Psychiatric Clinic Sample With Autism Spectrum Disorder and/or Attention-Deficit Hyperactivity Disorder: A Cross-Sectional Study

Extant literature suggests that autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD) are risk factors for internet addiction (IA). The present cross-sectional study explored the prevalence of IA among 132 adolescents with ASD and/or ADHD in a Japanese psychiatric clinic using Young's Internet Addiction Test. The prevalence of IA among adolescents with ASD alone, with ADHD alone and with comorbid ASD and ADHD were 10.8, 12.5, and 20.0%, respectively. Our results emphasize the clinical importance of screening and intervention for IA when mental health professionals see adolescents with ASD and/or ADHD in psychiatric services.

Relative age within the school year and diagnosis of attention-deficit hyperactivity disorder: a nationwide population-based study

BACKGROUND

Findings are mixed on the relationship between attention-deficit hyperactivity disorder (ADHD) and younger relative age in the school year. We aimed to investigate whether relative age is associated with ADHD diagnosis in a country where prescribing rates are low and whether any such association has changed over time or relates to comorbid disorders (eg, conduct disorder [CD], oppositional defiant disorder [ODD], or learning disorder [LD]).

METHODS

We used nationwide population-based registers to identify all Finnish children born between Jan 1, 1991, and Dec 31, 2004, who were diagnosed with ADHD from age 7 years onwards (age of starting school). We calculated incidence ratios to assess the inter-relations between relative age within the school year, age at ADHD diagnosis, and year of diagnosis (1998-2003 vs 2004-11).

FINDINGS

Between Jan 1, 1998, and Dec 31, 2011, 6136 children with ADHD were identified. Compared with the oldest children in the school year (ie, those born between January and April), the cumulative incidence of an ADHD diagnosis was greatest for the youngest children (ie, those born between September and December); for boys the incidence ratio was 1·26 (95% CI 1·18-1·35; p<0·0001) and for girls it was 1·31 (1·12-1·54; p=0·0007). The association between relative age and age at ADHD diagnosis reflected children diagnosed before age 10 years, and the strength of this association increased during recent years (2004-11). Thus, compared with children born between January and April, for those born between May and August, the ADHD incidence ratio was 1·37 (95% CI 1·24-1·53; p<0·0001) and for those born between September and December, the incidence ratio was 1·64 (1·48-1·81; p<0·0001). The relative age effect was not accounted for by comorbid disorders such as CD, ODD, or LD.

INTERPRETATION

In a health service system with low prescribing rates for ADHD, a younger relative age is associated with an increased likelihood of receiving a clinical diagnosis of ADHD. This effect has increased in recent years. Teachers, parents, and clinicians should take relative age into account when considering the possibility of ADHD in a child or encountering a child with a pre-existing diagnosis.

FUNDING

Academy of Finland, Finnish Medical Foundation, Orion Pharma Foundation, Finnish Cultural Foundation.

Parental psychopathology and offspring attention-deficit/hyperactivity disorder in a nationwide sample

OBJECTIVE

To study the associations between a wide range of parental psychiatric disorders and offspring attention-deficit/hyperactivity disorder (ADHD).

METHOD

This study is based on a nested case-control design. The association between parental registered psychiatric diagnoses and offspring ADHD was examined adjusting for socioeconomic and prenatal factors. Data was linked from Finnish nationwide registers. The cases (n = 10,409) were all the children born between years 1991 and 2005 in Finland and diagnosed with ADHD by the end of 2011. Four controls without ADHD (n = 39,124) were matched for every case by sex, age and place of birth. Main outcomes were adjusted odds ratio (aOR) for parental diagnosis of cases vs controls. Analyses were further stratified by sex. Disorders diagnosed before and after birth were analyzed separately.

RESULTS

The odds ratio for ADHD increased when only mother (aOR 2.2, 95% CI 2.0-2.3), only father (aOR 1.7, 95% CI 1.6-1.8) and both parents (aOR 3.6, 95% CI 3.3-4.0) were diagnosed. Maternal diagnosis showed stronger association than paternal. The weight of association between several parental disorders and offspring ADHD were similar. Maternal psychopathology overall showed stronger associations with girls than boys with ADHD. The diagnoses registered after birth did not show stronger association than the diagnoses registered before.

CONCLUSIONS

Maternal psychopathology showing stronger association than paternal implies that environmental factors or their interaction with genetic factors partly mediates the risk of parental psychopathology. Similar associations between several maternal psychiatric disorders and offspring ADHD points towards the need for investigating some common mother-related risk factors.

Register-based study of the incidence, comorbidities and demographics of obsessive-compulsive disorder in specialist healthcare

BACKGROUND

Incidence of obsessive-compulsive disorder (OCD) has been suspected to increase but nationwide epidemiological studies are limited. This study aims to examine sex-specific incidence time trends and characterize psychiatric and neurodevelopmental comorbidities and sociodemographic risk factors of OCD in specialist healthcare in Finland.

METHODS

A nationwide register-based study using data from four Finnish registers identified 3372 OCD cases and 13,372 matched controls (1:4). Cumulative incidence in subjects born between 1987 and 2001 was estimated at ages of 10, 15, 20 and 23 years. Conditional logistic regression was used to examine the sociodemographic factors.

RESULTS

The cumulative incidence of OCD was 0.4% by age 23. Incidence by age 15 among three cohorts increased from 12.4 to 23.7 /10000 live born males and 8.5 to 28.0 /10000 live born females. 73% of the sample had a comorbid condition. Males were significantly more comorbid with psychotic and developmental disorders; females were more comorbid with depressive and anxiety disorders (p <0.001). Higher maternal SES was associated with an increased risk of OCD (OR 1.4; 95% CI 1.1-1.6).

CONCLUSIONS

These findings suggest that incidence of treated OCD in specialist healthcare has increased. The reason may be increased awareness and rate of referrals but a true increase cannot be ruled out. Further research on risk factors of OCD is warranted.

ADHD, comorbid disorders and psychosocial functioning: How representative is a child cohort study? Findings from a national patient registry

BACKGROUND

Cohort studies often report findings on children with Attention Deficit Hyperactivity Disorder (ADHD) but may be biased by self-selection. The representativeness of cohort studies needs to be investigated to determine whether their findings can be generalised to the general child population. The aim of the present study was to examine the representativeness of child ADHD in the Norwegian Mother and Child Cohort Study (MoBa).

METHODS

The study population was children born between January 1, 2000 and December 31, 2008 registered with hyperkinetic disorders (hereafter ADHD) in the Norwegian Patient Registry during the years 2008-2013, and two groups of children with ADHD were identified in: 1. MoBa and 2. The general child population. We used the multiaxial International Classification of Diseases (ICD-10) and compared the proportions of comorbid disorders (axes I-III), abnormal psychosocial situations (axis V) and child global functioning (axis VI) between these two groups. We also compared the relative differences in the multiaxial classifications for boys and girls and for children with/without axis I comorbidity, respectively in these two groups of children with ADHD.

RESULTS

A total of 11 119 children were registered with ADHD, with significantly fewer in MoBa (1.45%) than the general child population (2.11%), p < 0.0001. The proportions of comorbid axis I, II, and III disorders were low, with no significant group differences. Compared with the general child population with ADHD, children with ADHD in MoBa were registered with fewer abnormal psychosocial situations (axis V: t = 7.63, p < .0001; d = -.18) and better child global functioning (axis VI: t = 7.93, p < 0.0001; d = .17). When analysing relative differences in the two groups, essentially the same patterns were found for boys and girls and for children with/without axis I comorbidity.

CONCLUSIONS

Self-selection was found to affect the proportions of ADHD, psychosocial adversity and child global functioning in the cohort. However, the differences from the general population were small. This indicates that studies on ADHD and multiaxial classifications in MoBa, as well as other cohort studies with similar self-selection biases, may have reasonable generalisability to the general child population.