Long-term prenatal exposure to paracetamol is associated with DNA methylation differences in children diagnosed with ADHD

BACKGROUND

Epidemiological studies have shown that long-term exposure to paracetamol during pregnancy is associated with attention-deficit/hyperactivity disorder (ADHD). The mechanism by which paracetamol may modulate the increased risk of developing ADHD is currently unknown. We have conducted an epigenome-wide association study (n = 384 cord blood samples) and investigated whether prenatal exposure to paracetamol is associated with DNA methylation in children diagnosed with ADHD.

RESULTS

Analyses identified significant differences in DNA methylation (n = 6211 CpGs) associated with prenatal exposure to paracetamol for more than 20 days in children diagnosed with ADHD compared to controls. In addition, these samples were differentially methylated compared to samples with ADHD exposed to paracetamol for less than 20 days (n = 2089 CpGs) and not exposed to paracetamol (n = 193 CpGs). Interestingly, several of the top genes ranked according to significance and effect size have been linked to ADHD, neural development, and neurotransmission. Gene ontology analysis revealed enrichment of pathways involved in oxidative stress, neurological processes, and the olfactory sensory system, which have previously been implicated in the etiology of ADHD.

CONCLUSIONS

These initial findings suggest that in individuals susceptible to ADHD, prenatal long-term exposure to paracetamol is associated with DNA methylation differences compared to controls.

Stability and change in etiological factors for alcohol use disorder and major depression

Alcohol use disorder (AUD) and major depressive disorder (MDD) are often comorbid. It is not understood how genetic risk factors for these disorders relate to each other over time and to what degree they are stable. Age-dependent characteristics of the disorders indicate that different genetic factors could be relevant at different stages of life, and MDD may become increasingly correlated with AUD over time. DSM-IV diagnoses of AUD and MDD were assessed by interviews of 2,801 young adult twins between 1999 and 2004 (T1) and 2,284 of the same twins between 2010 and 2011 (T2). Stability, change, and covariation were investigated in longitudinal biometric models. New genetic factors explained 56.4% of the genetic variance in AUD at T2. For MDD, there was full overlap between genetic influences at T1 and T2. Genetic risk factors for MDD were related to AUD, but their association with AUD did not increase over time. Thus, genetic risk factors for AUD, but not MDD, vary with age, suggesting that AUD has age-dependent heritable etiologies. Molecular genetic studies of AUD may therefore benefit from stratifying by age. The new genetic factors in AUD were not related to MDD. Environmental influences on the 2 disorders were correlated in middle, but not in young adulthood. The environmental components for AUD correlated over time (r = .27), but not for MDD. Environmental influences on AUD can have long-lasting effects, and the effects of preventive efforts may be enduring. Environment influences seem to be largely transient. (PsycINFO Database Record

Co-Occurrence of ODD and CD in Preschool Children With Symptoms of ADHD

OBJECTIVE

Patterns of co-occurrence between ADHD, Oppositional Defiant Disorder (ODD), and Conduct Disorder (CD) were examined in a sample of non-referred preschool children. ADHD subtypes and sex differences were also explored.

METHOD

Children aged 3.5 years ( n = 1,048) with high scores on ADHD characteristics were recruited from the Norwegian Mother and Child Cohort Study and clinically assessed, including a semi-structured psychiatric interview.

RESULTS

In children with ADHD, concurrent ODD was present more often than CD (31% vs. 10%), but having ADHD gave higher increase in the odds of CD than of ODD (ODD: odds ratio [OR] = 6.7, 95% confidence interval [CI] = [4.2, 10.8]; CD: OR = 17.6, 95% CI = [5.9, 52.9]). We found a greater proportion of children having the combined ADHD subtype as well as more severe inattentiveness among children with co-occurring CD compared with ODD. Sex differences were minor.

CONCLUSION

There are important differences in co-occurring patterns of ODD and CD in preschool children with ADHD.

The influence of parental concern on the utility of autism diagnostic instruments

The parental report-based Autism Diagnostic Interview-Revised (ADI-R) and the clinician observation-based Autism Diagnostic Observation Schedule (ADOS) have been validated primarily in U.S. clinics specialized in autism spectrum disorder (ASD), in which most children are referred by their parents because of ASD concern. This study assessed diagnostic agreement of the ADOS-2 and ADI-R toddler algorithms in a more broadly based sample of 679 toddlers (age 35-47 months) from the Norwegian Mother and Child Cohort. We also examined whether parental concern about ASD influenced instrument performance, comparing toddlers identified based on parental ASD concern (n = 48) and parent-reported signs of developmental problems (screening) without a specific concern about ASD (n = 400). The ADOS cutoffs showed consistently well-balanced sensitivity and specificity. The ADI-R cutoffs demonstrated good specificity, but reduced sensitivity, missing 43% of toddlers whose parents were not specifically concerned about ASD. The ADI-R and ADOS dimensional scores agreed well with clinical diagnoses (area under the curve ≥ 0.85), contributing additively to their prediction. On the ADI-R, different cutoffs were needed according to presence or absence of parental ASD concern, in order to achieve comparable balance of sensitivity and specificity. These results highlight the importance of taking parental concern about ASD into account when interpreting scores from parental report-based instruments such as the ADI-R. While the ADOS cutoffs performed consistently well, the additive contributions of ADI-R and ADOS scores to the prediction of ASD diagnosis underscore the value of combining instruments based on parent accounts and clinician observation in evaluation of ASD. Autism Res 2017, 10: 1672-1686. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Pre-pregnancy mental distress and musculoskeletal pain and sickness absence during pregnancy - a twin cohort study

Background

Sickness absence (SA) among pregnant women is high. The aim of this study was to examine whether factors known to predict SA in general also predict SA during pregnancy by estimating the association between prior mental distress and musculoskeletal pain and SA during pregnancy, and to assess the influence of familial (genetic and shared environmental) factors. In this prospective cohort study, data from 2076 female twins born 1967-79 who participated in a questionnaire study in 1998 were linked to register data on SA and childbirth during the years 1998-2008. Baseline measures included mental distress (symptoms of anxiety and depression; SCL-5) and musculoskeletal pain (lumbar spine, neck/shoulder and/or persisting muscular pain). SA was measured as a ratio of days on SA divided by potential working days. Negative binomial regression was performed for individual and within-pair effects. Musculoskeletal pain, but not mental distress, was prospectively associated with overall SA during pregnancy in the adjusted individual-level analyses. With each standard deviation increase in musculoskeletal pain, SA granted for any disorder increased with 12% (IRR 1.12, 95% CI = 1.07-1.17) and SA granted for pregnancy related disorders increased with 9% (IRR 1.09, 95% CI = 1.02-1.17). Within-pair estimates were similar, suggesting little or no familial confounding. Women with previous musculoskeletal pain are at increased risk of SA during pregnancy, whereas no increased risk in women with previous symptoms of mental distress could be demonstrated. SA during pregnancy seems partly to be associated with different factors than SA in general.

Genetic and Environmental Contributions to the Association Between Cannabis Use and Psychotic-Like Experiences in Young Adult Twins

To investigate contributions of genetic and environmental risk factors and possible direction of causation for the relationship between symptoms of cannabis use disorders (CUD) and psychotic-like experiences (PLEs), a population-based sample of 2793 young adult twins (63.5% female, mean [range] age 28.2 [19-36] y) were assessed for symptoms of CUD and PLEs using the Composite International Diagnostic Interview. Latent risk of having symptoms of CUD or PLEs was modeled using Item Response Theory. Co-twin control analysis was performed to investigate effect of familiar confounding for the association between symptoms of CUD and PLEs. Biometric twin models were fitted to estimate the heritability, genetic and environmental correlations, and direction for the association. Lifetime use of cannabis was reported by 10.4 % of the twins, and prevalence of PLEs ranged from 0.1% to 2.2%. The incidence rate ratio of PLEs due to symptoms of CUD was 6.3 (95% CI, 3.9, 10.2) in the total sample and 3.5 (95% CI, 1.5, 8.2) within twin pairs. Heritability estimates for symptoms of CUD were 88% in men and women, and for PLEs 77% in men and 43% in women. The genetic and environmental correlations between symptoms of CUD and PLEs were 0.55 and 0.52, respectively. The model allowing symptoms of CUD to cause PLEs had a better fit than models specifying opposite or reciprocal directions of causation. The association between symptoms of CUD and PLEs is explained by shared genetic and environmental factors and direct effects from CUD to risk for PLEs.

The association between personality disorders with alcohol use and misuse: A population-based twin study

BACKGROUND

A clearer understanding of the etiological overlap between DSM-IV personality disorders (PDs) and alcohol use (AU) and alcohol use disorder (AUD) is needed. To our knowledge, no study has modeled the association between all 10 DSM-IV PDs and lifetime AU and AUD. The aim of the present study is to identify which PDs are most strongly associated with the phenotypic, genetic, and environmental risks of lifetime AU and AUD, and to determine if these associations are stable across time.

METHODS

Participants were Norwegian twins assessed at two waves. At Wave 1, 2801 twins were assessed for all 10 DSM-IV PD criteria, lifetime AU, and DSM-IV AUD criteria. At Wave 2, six of the 10 PDs were again assessed along with AU and AUD among 2393 twins. Univariate and multiple logistic regressions were run. Significant predictors were further analyzed using bivariate twin Cholesky decompositions.

RESULTS

Borderline and antisocial PD criteria were the strongest predictors of AU and AUD across the two waves. Despite moderate phenotypic and genetic correlations, genetic variation in these PD criteria explained only 4% and 3% of the risks in AU, and 5% to 10% of the risks in AUD criteria, respectively. At Wave 2, these estimates increased to 8% and 23% for AU, and 17% and 33% for AUD.

CONCLUSIONS

Among a large Norwegian twin sample, borderline and antisocial PD criteria were the strongest predictors of the phenotypic and genotypic liability to AU and AUD. This effect remained consistent across time.

Effects of Sample Handling and Analytical Procedures on Thyroid Hormone Concentrations in Pregnant Women's Plasma

BACKGROUND

Maternal thyroid function is a critical mediator of fetal brain development. Pregnancy-related physiologic changes and handling conditions of blood samples may influence thyroid hormone biomarkers. We investigated the reliability of thyroid hormone biomarkers in plasma of pregnant women under various handling conditions.

METHODS

We enrolled 17 pregnant women; collected serum and plasma were immediately frozen. Additional plasma aliquots were subjected to different handling conditions before the analysis of thyroid biomarkers: storage at room temperature for 24 or 48 hours before freezing and an extra freeze-thaw cycle. We estimated free thyroid hormone indices in plasma based on T3 uptake.

RESULTS

High correlations between plasma and serum (>0.94) and intraclass correlation coefficients for plasma handling conditions (0.96 to 1.00) indicated excellent reliability for all thyroid hormone biomarkers.

CONCLUSION

Delayed freezing and freeze-thaw cycles did not affect reliability of biomarkers of thyroid function in plasma during pregnancy. See video abstract at, http://links.lww.com/EDE/B180.

The Genetic and Environmental Sources of Resemblance Between Normative Personality and Personality Disorder Traits

Recent work has suggested a high level of congruence between normative personality, most typically represented by the "big five" factors, and abnormal personality traits. In 2,293 Norwegian adult twins ascertained from a population-based registry, the authors evaluated the degree of sharing of genetic and environmental influences on normative personality, assessed by the Big Five Inventory (BFI), and personality disorder traits (PDTs), assessed by the Personality Inventory for DSM-5-Norwegian Brief Form (PID-5-NBF). For four of the five BFI dimensions, the strongest genetic correlation was observed with the expected PID-5-NBF dimension (e.g., neuroticism with negative affectivity [+], conscientiousness with disinhibition [-]). However, neuroticism, conscientiousness, and agreeableness had substantial genetic correlations with other PID-5-NBF dimensions (e.g., neuroticism with compulsivity [+], agreeableness with detachment [-]). Openness had no substantial genetic correlations with any PID-5-NBF dimension. The proportion of genetic risk factors shared in aggregate between the BFI traits and the PID-5-NBF dimensions was quite high for conscientiousness and neuroticism, relatively robust for extraversion and agreeableness, but quite low for openness. Of the six PID-5-NBF dimensions, three (negative affectivity, detachment, and disinhibition) shared, in aggregate, most of their genetic risk factors with normative personality traits. Genetic factors underlying psychoticism, antagonism, and compulsivity were shared to a lesser extent, suggesting that they are influenced by etiological factors not well indexed by the BFI.

The quality of severe mental disorder diagnoses in a national health registry as compared to research diagnoses based on structured interview

BACKGROUND

Utilization of diagnostic information from national patient registries rests on the quality of the registered diagnoses. We aimed to investigate the agreement and consistency of diagnoses of psychotic and bipolar disorders in the Norwegian Patient Registry (NPR) compared to structured interview-based diagnoses given as part of a clinical research project.

METHODS

Diagnostic data from NPR were obtained for the period 01.01.2008-31.12.2013 for all patients who had been included in the Thematically Organized Psychosis (TOP) study between 18.10.2002 and 01.09.2014 with a Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) diagnosis of schizophrenia (n = 537), delusional disorder (n = 48), schizoaffective disorder (n = 118) or bipolar disorder (n = 408). Diagnostic agreement between the primary DSM-IV diagnosis in TOP and the International Classification of Diseases, 10th revision (ICD-10) diagnoses in NPR was evaluated using Cohen's unweighted nominal kappa (κ). Diagnostic consistency was calculated as the proportion of all registered severe mental disorder diagnoses in NPR that were equivalent to the primary diagnosis given in the TOP study.

RESULTS

The proportion of patients registered with the equivalent ICD-10 diagnosis as the primary DSM-IV diagnosis given in TOP was 84.2% for the schizophrenia group, 68.8% for the delusional disorder group, 76.3% for the schizoaffective disorder group, and 78.4% for the bipolar disorder group. Diagnostic agreement was good for schizophrenia (κ = 0.74) and bipolar disorder (κ = 0.72), fair for schizoaffective disorder (κ = 0.63), and poor for delusional disorder (κ = 0.39). Among patients with DSM-IV schizophrenia, 4.7% were diagnosed with ICD-10 bipolar disorder, and among patients with DSM-IV bipolar disorder, 2.5% were diagnosed with ICD-10 schizophrenia. Diagnostic consistency was 84.9% for schizophrenia, 59.1% for delusional disorder, 65.9% for schizoaffective disorder, and 91.0% for bipolar disorder.

CONCLUSIONS

When compared to research-based diagnoses, clinical diagnoses of schizophrenia and bipolar disorder in the NPR are accurate and consistent, with minimal diagnostic overlap between the two disorders.

Smoking in Pregnancy and Child ADHD

BACKGROUND AND OBJECTIVE

There is a well-documented association between maternal smoking during pregnancy and offspring attention-deficit/hyperactivity disorder (ADHD). The degree to which this reflects causal intrauterine effects or is due to unmeasured confounding is not clear. We sought to compare the association between maternal smoking during pregnancy and offspring ADHD with the associations with paternal smoking, grandmother's smoking when pregnant with mother, and maternal smoking in previous pregnancies. Each of these exposures is expected to be influenced by much of the same confounding factors as maternal smoking during pregnancy, but cannot have direct intrauterine effects. A sibling control design was also used.

METHODS

The current study used data from the Norwegian Mother and Child Cohort Study (n > 100 000 children). Mothers and fathers reported on smoking during pregnancy, and mothers reported on smoking in previous pregnancies and their mother's smoking when pregnant with them. Mothers reported on child ADHD symptoms at 5 years of age. Information about child ADHD diagnosis was obtained from the Norwegian Patient Registry.

RESULTS

Maternal smoking during pregnancy was not more strongly associated with offspring ADHD diagnosis than was paternal smoking, grandmother's smoking when pregnant with mother, or maternal smoking in previous pregnancies. Sibling control analyses showed no association between maternal smoking in pregnancy and child ADHD symptoms among siblings discordant for maternal smoking.

CONCLUSIONS

These results suggest that the association between maternal smoking during pregnancy and offspring ADHD is not due to causal intrauterine effects, but reflects unmeasured confounding.

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.

Impact of Pre-Pregnancy BMI on B Vitamin and Inflammatory Status in Early Pregnancy: An Observational Cohort Study

Maternal nutrition and inflammation have been suggested as mediators in the development of various adverse pregnancy outcomes associated with maternal obesity. We have investigated the relation between pre-pregnancy BMI, B vitamin status, and inflammatory markers in a group of healthy pregnant women. Cobalamin, folate, pyridoxal 5′-phosphate, and riboflavin; and the metabolic markers homocysteine, methylmalonic acid, and 3-hydroxykynurenine/xanthurenic acid ratio (HK/XA); and markers of cellular inflammation, neopterin and kynurenine/tryptophan ratio (KTR) were determined in pregnancy week 18 and related to pre-pregnancy body mass index (BMI), in 2797 women from the Norwegian Mother and Child Cohort Study (MoBa). Pre-pregnancy BMI was inversely related to folate, cobalamin, pyridoxal 5′-phosphate (PLP), and riboflavin (p < 0.001), and associated with increased neopterin and KTR levels (p < 0.001). Inflammation seemed to be an independent predictor of low vitamin B6 status, as verified by low PLP and high HK/XA ratio. A high pre-pregnancy BMI is a risk factor for low B vitamin status and increased cellular inflammation. As an optimal micronutrient status is vital for normal fetal development, the observed lower B vitamin levels may contribute to adverse pregnancy outcomes associated with maternal obesity and B vitamin status should be assessed in women with high BMI before they get pregnant.

Language Delay in 3-Year-Old Children With ADHD Symptoms

OBJECTIVE

Little is known about cognition in preschoolers with ADHD and language delay (LD). The objective was to investigate cognitive functions in preschoolers with ADHD symptoms and LD compared with children with ADHD symptoms only and to estimate the frequency of children with ADHD symptoms, co-occurring language delay, and delays on cognitive measures.

METHOD

Participants were recruited from the Norwegian Mother and Child Cohort Study. The teacher report of expressive language and the cognitive tests from 119 3-year-old children with parent reported ADHD symptoms and LD were compared with those of 258 children with ADHD symptoms only.

RESULTS

The ADHD + LD group performed significantly worse than the ADHD group on most language-related measures. There were no differences between the groups on most nonverbal measures. Single measures had a limited potential of differentiating between the groups.

CONCLUSION

ADHD symptoms and co-occurring LD in preschoolers were characterized by cognitive deficits associated with both disorders, not with global neurodevelopmental delay.

Does low alcohol use increase the risk of sickness absence? A discordant twin study

Background

Results from observational studies suggest that people who drink little or no alcohol are less healthy than medium drinkers. This has been demonstrated for many different measures of health, including sick leave. However, whether these associations are causal or due to confounding remains to be clarified. The aim of this study was to use a discordant twin design to determine whether the increased level of sick leave associated with a low level of alcohol consumption, as compared to those with a medium level of consumption, reflects a causal mechanism or is due to genetic or environmental confounding.

Methods

Six thousand seven hundred thirty-four young adult twins from the Norwegian Institute of Public Health’s twin panel were in 1998 assessed for frequency of alcohol use and binge drinking. Data were linked to the Norwegian National Insurance Administration’s recordings of sick leave over a 10 year period. The associations between alcohol consumption and sick leave were first estimated in the total study population, and then within di- and monozygotic twin pairs discordant for alcohol use.

Results

Compared to medium consumption, both low and high alcohol consumption was associated with increased risk of sick leave. When low level drinkers were compared to medium level drinkers in a discordant twin design, the results were consistent with the association being due to genetic confounding rather than a causal effect.

Conclusions

The increased level of sick leave observed with low level drinkers seems to be mainly explained by confounding from genetic factors. In all observational studies of the relationship between alcohol consumption and health, one should be aware that important genetic confounders are likely to influence the results.

Mood, anxiety, and alcohol use disorders and later cause-specific sick leave in young adult employees

BACKGROUND

Mental disorders strongly influence work capability in young adults, but it is not clear which disorders that are most strongly associated with sick leave, and which diagnoses that are stated on the sick leave certificates. Better knowledge of the impairments associated with different mental disorders is needed for optimal planning of interventions and prioritization of health services. In the current study, we investigate the prospective associations between eight mood, anxiety, and alcohol use disorders, and later sick leave granted for mental, somatic, or any disorder.

METHODS

Lifetime mental disorders were assessed by structured diagnostic interviews in 2,178 young adults followed for eight years with registry data on sick leave. Relative risk ratios were estimated for the associations between each mental disorder and the different forms of sick leave.

RESULTS

All included diagnoses were associated with later sick leave. In adjusted analyses, major depressive disorder and generalized anxiety disorder were the strongest predictors of sick leave granted for mental disorders, whereas social anxiety disorder and specific phobia were the strongest predictors of sick leave granted for somatic disorders. Specific phobia and major depressive disorder had the highest attributable fractions for all-cause sick leave.

CONCLUSIONS

Mood and anxiety disorders constituted independent risk factors for all cause sick leave, whereas alcohol use disorders seemed to be of less importance in young adulthood. Disorders characterised by distress were most strongly associated with sick leave granted for mental disorders, whereas disorders characterised by fear primarily predicted sick leave granted for somatic conditions. A large part of all sick leave is related to specific phobia, due to the high prevalence of this disorder. The impairment associated with this common disorder may be under-acknowledged, and it could decrease work capacity among individuals with somatic disorders. This disorder has good treatment response and may be overlooked as a target for interventions aimed at prevention of sick leave.

Musculoskeletal pain and work absence – a 10 year follow-up study of Norwegian young adult twins

Background and aims: Sickness absence (SA) and disability pension (DP) are increasingly recognized asmajor public problems. Musculoskeletal disorders are among the most common diagnoses set by physiciansgranting SA and DP. Results from recent twin studies have established that SA and DP are influencednot only by environmental and social factors, but also moderately to substantially by genes. The aim of thecurrent study was to examine to what degree musculoskeletal complaints in young adults predict SA andDP, including SA granted for other diagnoses. As the participants were twins, we were able to performwithin pair analyses, to see if the associations between musculoskeletal pain and later DP or SA were confoundedby unmeasured genetic and shared environmental factors.Materials and methods: The Norwegian twin registry includes a questionnaire conducted in 1998. Fromthis, we included three measures of recurrent pain (lower back, neck/shoulders and muscular) as well assymptoms of anxiety and depression (measured by the Symptom Checklist-5 (SCL-5)). The questionnairehas been linked to highly reliable official registries on SA and DP, as well as a range of sociodemographicvariables, for a ten-year follow up period. We applied logistic (DP as dependent variable) and binomialregression (SA as dependent variable) analyses to explore the relationship between musculoskeletal painand DP and SA. In the final models, we adjusted for sociodemographic factors and symptoms of anxietyand depression. Differences between twins in a pair were explored by applying fixed effect models. Allanalyses were conducted using STATA version 13.1.Results: The final sample of 7,626 twins included 3,055 complete pairs (488 monozygotic (MZ) male, 349dizygotic (DZ) male, 747 MZ female, 589 DZ female, and 882 opposite sex twin pairs) and 1,516 singletons.By the end of follow up, 181 subjects (44 men and 137 women) received DP, and 63.7% of the sample(47.4% of males and 76.0% of females) had at least one period of SA extending 16 days. Pain at any sitewas significantly associated with DP in both sexes. Any increase in the number of pain sites reported wasassociated with about a 60% increased risk for receiving DP (OR 1.6, 95% CI 1.4-1.9), and the strength ofthe association was only marginally reduced when adjusted for symptoms of mental disorders (1.4, 1.2-1.7). In the within pair analyses the effect was no longer significant, indicating possible confounding fromgenetic and shared environmental effects. As for all cause SA, musculoskeletal pain predicted SA independentlyof all measured confounders, and the results remained significant in the within pair analyses (IncidenceRate Ratio (IRR) 1.12, 95% CI 1.03-1.23).Conclusion: In young adults, musculoskeletal pain strongly predicted SA and DP for a 10 year follow-upperiod. Musculoskeletal pain was associated with higher levels of all cause SA, even within discordant MZtwin pairs. Our results indicate that interventions to prevent musculoskeletal pain in young adults canreduce levels of SA and DP.

Social inequalities in reception of social welfare support: A population based twin study

Social welfare support runs in families. Recent studies using Nordic registry data have found individualdifferences in genetic factors to be of substantial importance for medical benefits. However, to date there hasbeen no genetically informative studies on receiving social welfare support. To prevent young adults to notdrop out of the work life and become recipients of social welfare support, it is of substantial interest toclarify to what extent the familiarity of social welfare support is due to genetic or social differences betweenfamilies. We used data from the Historical-Event Database on 7,698 Norwegian twins born 1967-1979 toestimate the relative contribution of genetic factors, the effective familial environment (i.e. the “sharedenvironment”), and individual-specific environmental factors. We found that the two forms of familial risk,genetic and shared environmental, explained 39% and 45%, respectively, of the risk for receiving socialwelfare support among young Norwegian twins. Only 17% of the variance in risk factors could be explainedby individual-specific risk factors. It appears that risk for receiving social welfare support can to a greatextent be explained by environmental differences between families. Therefore prevention strategies targetingsocial inequalities between families would indeed be effective. Furthermore, genetic risk factors are alsoimportant in explaining risk for receiving social welfare support. These effects could be mediated throughheritable traits related to substance abuse, psychiatric disorders, and personality. Individual-specific risk factorswere of very little importance. Hence, with regard to receiving social welfare support, family matters.

Advantages of linking national registries with twin registries for epidemiological research

Linking national registries with twin data represents an opportunity to produce epidemiological research of<br />high quality. National registries contain information on a broad array of variables, some of which cannot be<br />measured reliably in regular health surveys. By taking kinship into consideration, twin studies have the<br />benefit of being able to identify confounding stemming from genetic or shared environmental sources. In<br />this paper, we use examples from our own interview and questionnaire-based twin studies from the Norwegian<br />Twin Registry (NTR) on mental disorders, alcohol use and socioeconomic status linked to registry<br />data on medical benefits to demonstrate the value. In the first example, we examined to what extent genetic<br />and environmental factors contributed to sick leave and disability pension and the association between these<br />two types of benefits. In the second example, we explored the genetic and environmental relationship<br />between personality disorders and sick leave. In the third example, a co-twin control design was applied to<br />explore whether there is a true protective relationship between moderate alcohol consumption and health.<br />The fourth example shows to what degree anxiety and depression are associated with later sick leave granted<br />for not only mental disorders, but also somatic disorders, adjusted for confounding by genetic and shared<br />environmental factors. In the fifth example, we address the socioeconomic gradient in sick leave, adjusting<br />for non-observed confounders associated with the family in a co-twin control design. Our examples illustrate<br />some of the potentials obtainable by linking national registries with twin data. The efforts that have been<br />made to create the NTR in Norway and the International Network of Twin Studies (INTR) internationally<br />make these types of linkage studies easier to conduct and available to more researchers. As there are still<br />many areas to explore, we encourage epidemiological researchers to make use of this possibility.

The Norwegian Twin Registry

The Norwegian Twin Registry (NTR) is a large population based twin cohort for research purposes. At present,<br />the registry has 14 692 complete twin pairs with information on zygosity and to varying degree information on<br />somatic and mental health, lifestyle and demographics. The registry covers birth years 1895-1960 and 1967-<br />1991. NTR was established in 2009, at the Norwegian Institute of Public Health, as a merger of three major<br />twin panels, the oldest originating in the 1960s. Since then Norwegian twin research has been a notable<br />contributor to twin research internationally. Norwegian twin researchers have published over 250 papers based<br />on Norwegian twin data, spanning a broad range of somatic and mental health phenotypes. In twin studies of<br />heritability a data structure with both variance within and between pairs is required. Therefore a large sample is<br />necessary, especially when studying rare diseases and conditions, and it is of vital importance to expand the<br />registry. NTR is actively recruiting new twins, both young and older, but declining response rates are a<br />challenge. The value of NTR is greatly enhanced through the linkage possibilities offered by Norway’s many<br />nationwide registries (medical, demographic, and socio-economic). Access to data is permitted by the NTR<br />steering group and will in most instances need permission from the Regional Ethics Committee.

A population-based study of help seeking and self-medication among trauma-exposed individuals

Epidemiologic studies of trauma highlight the imbalance between prevalence of psychiatric diagnoses and help seeking. We investigated prevalence and correlates of help seeking and self-medication in Norwegian adults with trauma history with a focus on common posttrauma outcomes of posttraumatic stress disorder (PTSD) and substance use disorders (alcohol or drug). Participants reporting at least 1 PTSD symptom (n = 307) were asked if they consulted with a doctor/another professional (help seeking) or used drugs/alcohol (self-medication) for trauma-related problems. PTSD, alcohol abuse or dependence (AUD), and drug use or dependence (DUD) were assessed via structured diagnostic interviews. Help seeking and self-medication were endorsed by 37.4% and 10.4% of the sample, respectively. As compared to the full sample, help seeking was endorsed at a greater rate in individuals with PTSD (χ2 = 8.59, p = .005) and at a lower rate in those with AUD (χ2 = 7.34, p < .004). Self-medication was more likely to be endorsed by individuals with PTSD than without PTSD (χ2 = 25.68, p < .001). In regression analyses, PTSD was associated with increased likelihood of self-medication (odds ratio [OR] = 4.56) and help seeking (OR = 2.29), while AUD was associated with decreased likelihood of help-seeking (OR = .29). When self-medication was included as a predictor, PTSD was no longer associated with help seeking, although AUD remained inversely associated. PTSD and AUDs have a nuanced relationship with formal help seeking as well as the use of substances to cope. Trauma-exposed individuals are likely engaging in adaptive and maladaptive coping strategies, the latter of which may be compounding distress. (PsycINFO Database Record

Sex differences in mortality among patients admitted with affective disorders in North Norway: a 33-year prospective register study

OBJECTIVE

Previous studies from North Norway showed significantly increased mortality in patients with schizophrenia and personality disorder. The aim of the present study was to investigate total and cause-specific mortality in inpatients with affective disorder in a 33-year follow-up cohort, with a specific focus on sex differences.

METHODS

Based on a hospital case register covering all admissions to psychiatric hospital in the two northernmost counties in Norway from 1980 to 2012, 790 men and 866 women with major depressive disorder and 331 men and 514 women with bipolar disorder were included. The cohort was linked to the Norwegian Cause of Death Registry. The relative mortality in men compared to women was tested using Cox regression with attained age as the time variable. The standardized mortality ratio (SMR) of the patients when compared to the general population in Norway was calculated.

RESULTS

Patients with affective disorders had twice the mortality of the general Norwegian population [SMR = 2.1, 95% confidence interval (CI): 1.9-2.3]. For major depressive disorder, the SMR for total mortality was higher among men (2.6, 95% CI: 2.2-3.0) than women (1.8, 95% CI: 1.5-2.1). For bipolar disorder, no difference was seen between men and women. The SMR for suicide among women showed an increasing trend throughout the period 1980-1990: 20.0 (95% CI: 10.4-38.4); 1991-2001: 27.0 (95% CI: 15.7-46.2); 2002-2012: 40.4 (95% CI: 23.0-71.2).

CONCLUSIONS

The substantially increased mortality in patients with affective disorders in Norway has been persistent over a period of 33 years, despite extensive reforms in psychiatric health care. Indications of increasing SMR for suicide in women call for further research.

The relationship between anxiety disorders and dimensional representations of DSM-IV personality disorders: A co-twin control study

BACKGROUND

There is substantial comorbidity between personality disorders (PDs) and anxiety disorders (ADs). Sharing of familial risk factors possibly explains the co-occurrence, but direct causal relationships between the disorders may also exist.

METHODS

2801 persons from 1391 twin pairs from the Norwegian Institute of Public Health Twin Panel were assessed for all DSM-IV PDs and ADs. Bivariate Poisson-regression analyses were performed to assess whether PDs predicted ADs at three different levels: All PDs combined, PDs combined within DSM-IV-clusters and each individual PD separately. Next, bivariate co-twin control analyses were executed within monozygotic (MZ) and dizygotic (DZ) twin pairs. A similar analytic strategy was employed in multivariate models including PDs as independent variables.

RESULTS

PDs predicted ADs at all levels of analysis in bivariate regression models. Bivariate co-twin control analyses demonstrated an increased risk of ADs in all PDs combined, all PD-clusters and in schizotypal, paranoid, borderline, antisocial, avoidant and dependent PD. In the multivariate regression model, all PD-clusters and schizotypal, borderline, avoidant and obsessive-compulsive PD predicted ADs. Only borderline and avoidant PD predicted ADs in the multivariate co-twin control analysis.

LIMITATIONS

Over-adjustment may explain the results from the multivariate analyses. The cross-sectional study design hampers causal inference.

CONCLUSIONS

Comorbidity between ADs and PDs can be largely accounted for by shared familial risk factors. However, the results are also consistent with a direct causal relationship partly explaining the co-occurrence. Our results indicate specific environmental factors for comorbidity of ADs and borderline and avoidant PDs that are not shared with other PDs.

Longitudinal associations between social anxiety disorder and avoidant personality disorder: A twin study

Social anxiety disorder (SAD) and avoidant personality disorder (AvPD) are frequently co-occurring psychiatric disorders with symptomatology related to fear of social situations. It is uncertain to what degree the 2 disorders reflect the same genetic and environmental risk factors. The current study addresses the stability and co-occurrence of SAD and AvPD, the factor structure of the diagnostic criteria, and genetic and environmental factors underlying the disorders at 2 time points. SAD and AvPD were assessed in 1,761 young adult female twins at baseline and 1,471 of these approximately 10 years later. Biometric models were fitted to dimensional representations of SAD and AvPD. SAD and AvPD were moderately and approximately equally stable from young to middle adulthood, with increasing co-occurrence driven by environmental factors. At the first wave, approximately 1 in 3 individuals with AvPD had SAD, increasing to 1 in 2 at follow-up. The diagnostic criteria for SAD and AvPD had a two-factor structure with low cross-loadings. The relationship between SAD and AvPD was best accounted for by a model with separate, although highly correlated (r = .76), and highly heritable (.66 and .71) risk factors for each disorder. Their genetic and environmental components correlated .84 and .59, respectively. The finding of partially distinct risk factors indicates qualitative differences in the etiology of SAD and AvPD. Genetic factors represented the strongest time-invariant influences, whereas environmental factors were most important at the specific points in time.