Shared genetic influences between attention-deficit/hyperactivity disorder (ADHD) traits in children and clinical ADHD

Intergenerational transmission of genetic risk for hyperactivity and inattention. Direct genetic transmission or genetic nurture?

Background

Hyperactivity and inattention, the symptoms of ADHD, are marked by high levels of heritability and intergenerational transmission. Two distinct pathways of genetic intergenerational transmission are distinguished: direct genetic transmission when parental genetic variants are passed to the child's genome and genetic nurture when the parental genetic background contributes to the child's outcomes through rearing environment. This study assessed genetic contributions to hyperactivity and inattention in childhood through these transmission pathways.

Methods

The sample included 415 families from the Quebec Newborn Twin Study. Twins' hyperactivity and inattention were assessed in early childhood by parents and in primary school by teachers. The polygenic scores for ADHD (ADHD-PGS) and educational attainment (EA-PGS) were computed from twins' and parents' genotypes. A model of intergenerational transmission was developed to estimate (1) the contributions of parents' and children's PGS to the twins' ADHD symptoms and (2) whether these variances were explained by genetic transmission and/or genetic nurture.

Results

ADHD-PGS explained up to 1.6% of the variance of hyperactivity and inattention in early childhood and primary school. EA-PGS predicted ADHD symptoms at both ages, explaining up to 1.6% of the variance in early childhood and up to 5.5% in primary school. Genetic transmission was the only significant transmission pathway of both PGS. The genetic nurture channeled through EA-PGS explained up to 3.2% of the variance of inattention in primary school but this association was non-significant.

Conclusions

Genetic propensities to ADHD and education predicted ADHD symptoms in childhood, especially in primary school. Its intergenerational transmission was driven primarily by genetic variants passed to the child, rather than by environmentally mediated parental genetic effects. The model developed in this study can be leveraged in future research to investigate genetic transmission and genetic nurture while accounting for parental assortative mating.

Maternal Fiber Intake During Pregnancy and Development of Attention-Deficit/Hyperactivity Disorder Symptoms Across Childhood: The Norwegian Mother, Father, and Child Cohort Study

BACKGROUND

Epidemiological studies suggest that maternal diet quality during pregnancy may influence the risk of neurodevelopmental disorders in offspring. Here, we investigated associations between maternal intake of dietary fiber and attention-deficit/hyperactivity disorder (ADHD) symptoms in early childhood.

METHODS

We used longitudinal data of up to 21,852 mother-father-child trios (49.2% female offspring) from MoBa (the Norwegian Mother, Father, and Child Cohort Study). The relationships between maternal fiber intake during pregnancy and offspring ADHD symptoms at ages 3, 5, and 8 years were examined using 1) multivariate regression (overall levels of ADHD symptoms), 2) latent class analysis (subclasses of ADHD symptoms by sex at each age), and 3) latent growth curves (longitudinal change in offspring ADHD symptoms). Covariates were ADHD polygenic scores in child and parents, total energy intake and energy-adjusted sugar intake, parental ages at birth of the child, and sociodemographic factors.

RESULTS

Higher maternal prenatal fiber intake was associated with lower offspring ADHD symptom scores at all ages (Bage3 = -0.14 [95% CI, -0.18 to -0.10]; Bage5 = -0.14 [95% CI, -0.19 to -0.09]; Bage8 = -0.14 [95% CI, -0.20 to -0.09]). Of the derived low/middle/high subclasses of ADHD symptoms, fiber was associated with lower risk of belonging to the middle subclass for boys and girls and to the high subclass for girls only (middle: odds ratioboys 0.91 [95% CI, 0.86 to 0.97]/odds ratiogirls 0.86 [95% CI, 0.81 to 0.91]; high: odds ratiogirls 0.82 [95% CI, 0.72 to 0.94]). Maternal fiber intake and rate of change in child ADHD symptoms across ages were not associated.

CONCLUSIONS

Low prenatal maternal fiber intake may increase symptom levels of ADHD in offspring during childhood, independently of genetic predisposition to ADHD, unhealthy dietary exposures, and sociodemographic factors.

Effects of an online mindfulness-based program for parents of children with attention deficit/hyperactivity disorder: a pilot, mixed methods study

Objectives

Online mindfulness-based program (MBP) for parents and families especially in clinical population is limited. Engagement and significant dropout are major issues in MBP implementation. This pilot study examined the effects of an online mindfulness-based program (MBP) on parents of children with Attention Deficit/Hyperactivity Disorder (ADHD).

Methods

A mixed methods study was applied to evaluate the effects of the MBP. A total of 43 parents were recruited and were randomly assigned into intervention group and waitlist control group. The online MBP lasted for 28 days, including 20 psychoeducation videos, homework audio guidance, and four instructor-led online group meetings. Purposive sampling was used to recruit parents who completed the program to share their experiences and suggestions for improving the program in semi-structured online interviews.

Results

Quantitative data showed that participants from the online MBP reported a medium to large effect on the reduction of child ADHD symptoms. In semi-structured interviews, participants reported positive experiences in their help seeking intention, and personal changes, such as emotion regulation and quality attention to their children. Participants further made suggestions for improvement.

Conclusions

The effect of online MBP is promising, and the program should be conducted. A large scale randomized controlled trial should be conducted to investigate the effects of MBP in clinical populations.

Clinical trial registration

ClinicalTrials.gov NCT05480423.

Unpacking the overlap between Autism and ADHD in adults: A multi-method approach

The overlap between Autism and Attention-Deficit Hyperactivity Disorder (ADHD) is widely observed in clinical settings, with growing interest in their co-occurrence in neurodiversity research. Until relatively recently, however, concurrent diagnoses of Autism and ADHD were not possible. This has limited the scope for large-scale research on their cross-condition associations, further stymied by a dearth of open science practices in the neurodiversity field. Additionally, almost all previous research linking Autism and ADHD has focused on children and adolescents, despite them being lifelong conditions. Tackling these limitations in previous research, 5504 adults - including a nationally representative sample of the UK (Study 1; n = 504) and a large pre-registered study (Study 2; n = 5000) - completed well-established self-report measures of Autism and ADHD traits. A series of network analyses unpacked the associations between Autism and ADHD at the individual trait level. Low inter-item connectivity was consistently found between conditions, supporting the distinction between Autism and ADHD as separable constructs. Subjective social enjoyment and hyperactivity-impulsivity traits were most condition-specific to Autism and ADHD, respectively. Traits related to attention control showed the greatest Bridge Expected Influence across conditions, revealing a potential transdiagnostic process underlying the overlap between Autism and ADHD. To investigate this further at the cognitive level, participants completed a large, well-powered, and pre-registered study measuring the relative contributions of Autism and ADHD traits to attention control (Study 3; n = 500). We detected age- and sex-related effects, however, attention control did not account for the covariance between Autism and ADHD traits. We situate our findings and discuss future directions in the cognitive science of Autism, ADHD, and neurodiversity, noting how our open datasets may be used in future research.

Co-development of attention deficit hyperactivity disorder and autistic trait trajectories from childhood to early adulthood

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) and autism, defined as traits or disorders, commonly co-occur. Developmental trajectories of ADHD and autistic traits both show heterogeneity in onset and course, but little is known about how symptom trajectories co-develop into adulthood.

METHODS

Using data from a population cohort, the Avon Longitudinal Study of Parents and Children, we examined correlations between ADHD and autistic traits across development, using the Social Communication Disorders Checklist and ADHD subscale of the Strengths and Difficulties Questionnaire. We modelled joint developmental trajectories of parent-reported ADHD and autistic traits between 4 and 25 years, then characterised trajectory classes based on sociodemographic, perinatal, psychopathology, cognition and social functioning variables and tested for associations with neurodevelopmental/psychiatric polygenic scores (PGS).

RESULTS

Three classes of trajectories were identified; a typically developing majority with low-stable ADHD-autistic traits (87%), a male-predominant subgroup with child/adolescent-declining traits (6%) and a subgroup with late-emerging traits (6%). ADHD-autistic trait correlations were greatest in young adulthood for the two nontypically developing classes. There were higher rates of emotional and conduct problems, low IQ, childhood seizures and poor social functioning in the declining and late-emerging classes compared to the low-stable class. Emotional, conduct and peer problems were more prevalent during childhood in the childhood/adolescent-declining class compared to other classes, but were more prevalent in young adulthood in the late-emerging class. Neurodevelopmental/psychiatric PGS also differed: both nontypically developing classes showed elevated ADHD PGS compared to the low-stable group, and the late-emerging group additionally showed elevated schizophrenia PGS and decreased executive function PGS, whereas the declining group showed elevated broad depression PGS.

CONCLUSIONS

Distinct patterns of ADHD-autism co-development are present across development in the general population, each with different characterising factors and genetic signatures as indexed by PGS.

Is quality of life related to high autistic traits, high ADHD traits and their Interaction? Evidence from a Young-Adult Community-Based twin sample

This study explored whether high autistic traits, high attention deficit hyperactivity disorder (ADHD) traits and their interaction were associated with quality of life (QoL) in a sample of 556 of young-adult twins (Mean age 22 years 5 months, 52% Female). Four participant groups were created: high autistic traits, high ADHD traits, high autistic/ADHD traits, and low ADHD/autistic traits. High autistic traits were associated with lower QoL across domains (physical, psychological, social, and environmental). High ADHD traits associated with lower physical, psychological, and environmental QoL. The interaction of autistic and ADHD traits was not significant in any domain. While mental health difficulties were associated with lower QoL, after accounting for mental health, most relationships between autistic traits, ADHD traits and QoL remained.

Polygenic and environmental determinants of tics in the Avon Longitudinal Study of Parents and Children

Tourette syndrome (TS) is caused by multiple genetic and environmental factors. Yet, little is known about the interplay of these factors in the occurrence of tics. We investigated whether polygenic risk score (PRS) of TS and pregnancy-related factors together enhance the explained variance of tic occurrence in the Avon Longitudinal Study of Parents and Children (N_cases  = 612; N_controls  = 4,201; 50% male; mean age 13.8 years). We included a cumulative adverse pregnancy risk score, maternal anxiety and depression, and maternal smoking and alcohol use during pregnancy. We investigated possible joint effects of genetic and pregnancy-related risk factors using a multivariable approach, and explored mediation effects between the pregnancy-related risk factors in explaining tic presence. The PRS and the cumulative adverse pregnancy risk score, maternal anxiety, or maternal depression explained significantly more variance of tic presence compared to models including only the PRS. Furthermore, we found that the cumulative adverse pregnancy risk score mediated the association between several pregnancy-related factors (maternal anxiety, depression, and smoking) and tics. The combination of a PRS and pregnancy-related risk factors explained more variance of tics in a general population cohort compared to studying these factors in isolation.

Examining the impact of ADHD polygenic risk scores on ADHD and associated outcomes: A systematic review and meta-analysis

Early identification of attention-deficit/hyperactivity disorder (ADHD) is critical for mitigating the many negative functional outcomes associated with its diagnosis. Because of the strong genetic basis of ADHD, the use of polygenic risk scores (PRS) could potentially aid in the early identification of ADHD and associated outcomes. Therefore, a systematic search of the literature on the association between ADHD and PRS in pediatric populations was conducted. All articles were screened for a priori inclusion and exclusion criteria, and, after careful review, 33 studies were included in our systematic review and 16 studies with extractable data were included in our meta-analysis. The results of the review were categorized into three common themes: the associations between ADHD-PRS with 1) the diagnosis of ADHD and ADHD symptoms 2) comorbid psychopathology and 3) cognitive and educational outcomes. Higher ADHD-PRS were associated with increased odds of having a diagnosis (OR = 1.37; p<0.001) and more symptoms of ADHD (β = 0.06; p<0.001). While ADHD-PRS were associated with a persistent diagnostic trajectory over time in the systematic review, the meta-analysis did not confirm these findings (OR = 1.09; p = 0.62). Findings showed that ADHD-PRS were associated with increased odds for comorbid psychopathology such as anxiety/depression (OR = 1.16; p<0.001) and irritability/emotional dysregulation (OR = 1.14; p<0.001). Finally, while the systematic review showed that ADHD-PRS were associated with a variety of negative cognitive outcomes, the meta-analysis showed no significant association (β = 0.08; p = 0.07). Our review of the available literature suggests that ADHD-PRS, together with risk factors, may contribute to the early identification of children with suspected ADHD and associated disorders.

Preschool development, temperament and genetic liability as early markers of childhood ADHD: A cohort study

Background

ADHD is associated with multiple adverse outcomes and early identification is important. The present study sets out to identify early markers and developmental characteristics during the first 30 months of life that are associated with ADHD 6 years later.

Methods

9201 participants from the prospective Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort were included. Outcome measures were parent-rated ADHD symptom scores (Strengths and Difficulties Questionnaire, SDQ) and ADHD diagnosis (Development and Wellbeing Assessment, DAWBA) at age 7. Seventeen putative markers were identified from previous literature and included: pre- and peri-natal risk factors, genetic liability (ADHD polygenic risk scores, PRS), early development, temperament scores and regulatory problems. Associations were examined using regression analysis.

Results

Univariable regression analysis showed that multiple early life factors were associated with future ADHD outcomes, even after controlling for sex and socio-economic status. In a multivariable linear regression model; temperament activity scores (B = 0.107, CI = 0.083-0.132), vocabulary delay (B = 0.605, CI = 0.211-0.988), fine motor delay (B = 0.693, CI = 0.360-1.025) and ADHD PRS (B = 0.184, CI = 0.074-0.294) were associated with future symptoms (R ² = 10.7%). In a multivariable logistic regression model, ADHD PRS (OR = 1.39, CI = 1.10-1.77) and temperament activity scores (OR = 1.09, CI = 1.04-1.16) showed association with ADHD diagnosis.

Conclusion

As well as male sex and lower socio-economic status, high temperament activity levels and motor and speech delays in the first 30 months of life, are associated with childhood ADHD. Intriguingly, given that genetic risk scores are known to explain little of the variance of ADHD outcomes, we found that ADHD PRS added useful predictive information. Future research needs to test whether predictive models incorporating aspects of early development and genetic risk scores are useful for predicting ADHD in clinical practice.

Toward Precision Medicine in ADHD

Attention-Deficit Hyperactivity Disorder (ADHD) is a complex and heterogeneous neurodevelopmental condition for which curative treatments are lacking. Whilst pharmacological treatments are generally effective and safe, there is considerable inter-individual variability among patients regarding treatment response, required dose, and tolerability. Many of the non-pharmacological treatments, which are preferred to drug-treatment by some patients, either lack efficacy for core symptoms or are associated with small effect sizes. No evidence-based decision tools are currently available to allocate pharmacological or psychosocial treatments based on the patient's clinical, environmental, cognitive, genetic, or biological characteristics. We systematically reviewed potential biomarkers that may help in diagnosing ADHD and/or stratifying ADHD into more homogeneous subgroups and/or predict clinical course, treatment response, and long-term outcome across the lifespan. Most work involved exploratory studies with cognitive, actigraphic and EEG diagnostic markers to predict ADHD, along with relatively few studies exploring markers to subtype ADHD and predict response to treatment. There is a critical need for multisite prospective carefully designed experimentally controlled or observational studies to identify biomarkers that index inter-individual variability and/or predict treatment response.

[The Genetic Basis of ADHD - An Update]

The Genetic Basis of ADHD - An Update Abstract. Genetic risks play an important role in the etiology of attention-deficit/hyperactivity disorder (ADHD). This review presents the current state of knowledge concerning the genetic basis of the disorder. It discusses the results of twin- and family-based studies, linkage and association studies as well as recent findings resulting from Genome Wide Association Studies (GWAS). Furthermore, it elaborates on the relevance of polygenic risk scores, rare variants, and epigenetic alterations, especially in light of findings on genetic pleiotropy in the context of frequent psychiatric comorbidities in patients with ADHD.

Early-Life Injuries and the Development of Attention-Deficit/Hyperactivity Disorder

Objective: To estimate phenotypic and familial association between early-life injuries and attention-deficit/hyperactivity disorder (ADHD) and the genetic contribution to the association using polygenic risk score for ADHD (PRS-ADHD) and genetic correlation analyses. Methods: Children born in Denmark between 1995-2010 (n = 786,543) were followed from age 5 years until a median age of 14 years (interquartile range: 10-18 years). Using ICD-10 diagnoses, we estimated hazard ratios (HRs) and absolute risks of ADHD by number of hospital/emergency ward-treated injuries by age 5. In a subset of ADHD cases and controls born 1995 to 2005 who had genetic data available (n = 16,580), we estimated incidence rate ratios (IRRs) for the association between PRS-ADHD and number of injuries before age 5 and the genetic correlation between ADHD and any injury before age 5. Results: Injuries were associated with ADHD (HR = 1.61; 95% CI, 1.55-1.66) in males (HR = 1.59; 1.53-1.65) and females (HR = 1.65; 1.54-1.77), with a dose-response relationship with number of injuries. The absolute ADHD risk by age 15 was 8.4% (3+ injuries) vs 3.1% (no injuries). ADHD was also associated with injuries in relatives, with a stronger association in first- than second-degree relatives. PRS-ADHD was marginally associated with the number of injuries in the general population (IRR = 1.06; 1.00-1.14), with a genetic correlation of 0.53 (0.21-0.85). Conclusions: Early-life injuries in individuals and their relatives were associated with a diagnosis of ADHD. However, even in children with the most injuries, more than 90% were not diagnosed with ADHD by age 15. Despite a low positive predictive value and that the impact of unmeasured factors such as parental behavior remains unclear, results indicate that the association is partly explained by genetics, suggesting that early-life injuries may represent or herald early behavioral manifestations of ADHD.

Mapping relationships between ADHD genetic liability, stressful life events, and ADHD symptoms in healthy adults

Attention-deficit/hyperactivity disorder (ADHD) symptoms are continuously distributed in the general population, where both genetic and environmental factors play roles. Stressful life events (SLEs) have been associated with ADHD diagnosis, but the relationship between ADHD genetic liability, SLEs, and ADHD symptoms in healthy individuals is less clear. Using a sample of 1,531 healthy adults (average age 26.9 years; 55.8% female), we investigated relationships between ADHD polygenic risk scores (ADHD-PRSs), SLEs, and ADHD symptoms in a general population sample. Confirming earlier findings in an overlapping sample, all SLE-measures assessed (lifetime SLEs, recent SLEs, and childhood trauma (CT)) were significantly correlated with total ADHD, inattention (IA), and hyperactivity-impulsivity (HI) scores (r² range = .08-.15; all p < .005). ADHD-PRSs was associated with HI (R²_best-fit  = .37%), lifetime SLEs (R²_best-fit  = .56%), and CT (R²_best-fit  = .40%). Mediation analyses showed that lifetime SLEs partially mediated the association between ADHD-PRSs and HI (indirect effect: β = 68.6, bias corrected accelerated 95% confident interval (BCa95%CI) [11.9, 131.0], p = .016, proportion mediated (P_M ) =19.5%), with strongest effects contributed by CT (β = 34.4, BCa95%CI [0.4, 76.5], p = .040, P_M  = 9.8%). On the other hand, HI partially mediated the association between the ADHD-PRSs and lifetime SLEs (β = 42.9, BCa95%CI [7.3, 83.9], p = .014, P_M  = 18.8%). Our study observed a complex relationship of genetic and environmental risk factors contributing to ADHD symptoms in the healthy adult population.

Exploring characteristic features of attention-deficit/hyperactivity disorder: findings from multi-modal MRI and candidate genetic data

The current study examined whether machine learning features best distinguishing attention-deficit/hyperactivity disorder (ADHD) from typically developing children (TDC) can explain clinical phenotypes using multi-modal neuroimaging and genetic data. Cortical morphology, diffusivity scalars, resting-state functional connectivity and polygenic risk score (PS) from norepinephrine, dopamine and glutamate genes were extracted from 47 ADHD and 47 matched TDC. Using random forests, classification accuracy was measured for each uni- and multi-modal model. The optimal model was used to explain symptom severity or task performance and its robustness was validated in the independent dataset including 18 ADHD and 18 TDC. The model consisting of cortical thickness and volume features achieved the best accuracy of 85.1%. Morphological changes across insula, sensory/motor, and inferior frontal cortex were also found as key predictors. Those explained 18.0% of ADHD rating scale, while dynamic regional homogeneity within default network explained 6.4% of the omission errors in continuous performance test. Ensemble of PS to optimal model showed minor effect on accuracy. Validation analysis achieved accuracy of 69.4%. Current findings suggest that structural deformities relevant to salience detection, sensory processing, and response inhibition may be robust classifiers and symptom predictors of ADHD. Altered local functional connectivity across default network predicted attentional lapse. However, further investigation is needed to clarify roles of genetic predisposition.

Association of etiological factors across the extreme end and continuous variation in disordered eating in female Swedish twins

BACKGROUND

Accumulating evidence suggests that many psychiatric disorders etiologically represent the extreme end of dimensionally distributed features rather than distinct entities. The extent to which this applies to eating disorders (EDs) is unknown.

METHODS

We investigated if there is similar etiology in (a) the continuous distribution of the Eating Disorder Inventory-2 (EDI-2), (b) the extremes of EDI-2 score, and (c) registered ED diagnoses, in 1481 female twin pairs at age 18 years (born 1992-1999). EDI-2 scores were self-reported at age 18. ED diagnoses were identified through the Swedish National Patient Register, parent-reported treatment and/or self-reported purging behavior of a frequency and duration consistent with DSM-IV criteria. We differentiated between anorexia nervosa (AN) and other EDs.

RESULTS

The heritability of the EDI-2 score was 0.65 (95% CI 0.61-0.68). The group heritabilities in DeFries-Fulker extremes analyses were consistent over different percentile-based extreme groups [0.59 (95% CI 0.37-0.81) to 0.65 (95% CI 0.55-0.75)]. Similarly, the heritabilities in liability threshold models were consistent over different levels of severity. In joint categorical-continuous models, the twin-based genetic correlation was 0.52 (95% CI 0.39-0.65) between EDI-2 score and diagnoses of other EDs, and 0.26 (95% CI 0.08-0.42) between EDI-2 score and diagnoses of AN. The non-shared environmental correlations were 0.52 (95% CI 0.32-0.70) and 0.60 (95% CI 0.38-0.79), respectively.

CONCLUSIONS

Our findings suggest that some EDs can partly be conceptualized as the extreme manifestation of continuously distributed ED features. AN, however, might be more distinctly genetically demarcated from ED features in the general population than other EDs.

Disentangling nature from nurture in examining the interplay between parent-child relationships, ADHD, and early academic attainment

BACKGROUND

Attention deficit hyperactivity disorder (ADHD) is highly heritable and is associated with lower educational attainment. ADHD is linked to family adversity, including hostile parenting. Questions remain regarding the role of genetic and environmental factors underlying processes through which ADHD symptoms develop and influence academic attainment.

METHOD

This study employed a parent-offspring adoption design (N = 345) to examine the interplay between genetic susceptibility to child attention problems (birth mother ADHD symptoms) and adoptive parent (mother and father) hostility on child lower academic outcomes, via child ADHD symptoms. Questionnaires assessed birth mother ADHD symptoms, adoptive parent (mother and father) hostility to child, early child impulsivity/activation, and child ADHD symptoms. The Woodcock-Johnson test was used to examine child reading and math aptitude.

RESULTS

Building on a previous study (Harold et al., 2013, Journal of Child Psychology and Psychiatry, 54(10), 1038-1046), heritable influences were found: birth mother ADHD symptoms predicted child impulsivity/activation. In turn, child impulsivity/activation (4.5 years) evoked maternal and paternal hostility, which was associated with children's ADHD continuity (6 years). Both maternal and paternal hostility (4.5 years) contributed to impairments in math but not reading (7 years), via impacts on ADHD symptoms (6 years).

CONCLUSION

Findings highlight the importance of early child behavior dysregulation evoking parent hostility in both mothers and fathers, with maternal and paternal hostility contributing to the continuation of ADHD symptoms and lower levels of later math ability. Early interventions may be important for the promotion of child math skills in those with ADHD symptoms, especially where children have high levels of early behavior dysregulation.

Prenatal and perinatal factors associated with ADHD risk in schoolchildren: EPINED epidemiological study

The aim of this study is to assess the relationship between pre- and perinatal factors and ADHD in a sample of scholars exploring differences between ADHD presentations and spectrum of severity. A total of 6720 scholars (aged 3-4 and 10-11) participated in a double-phase epidemiologic cross-sectional study (Epidemiological Study of Neurodevelopmental Disorders, EPINED), and a sample of 646 scholars (ADHD risk, ASD risk and controls without risk) were individually assessed in the second phase of the study. The ADHD diagnosis, based on DSM-5 criteria, was performed with the Kiddie-Schedule for Affective Disorders & Schizophrenia, Present & Lifetime Version. Associations for the different ADHD presentations between prenatal, perinatal and postnatal factors and ADHD (n = 168), subclinical ADHD (n = 88) and non-ADHD (n = 310) were analysed. Logistic regression models showed that gestational diabetes (p = 0.012), instrumental delivery (p = 0.011), family history of psychopathology (p = 0.033) and maternal ADHD phenotype (p = 0.023) were associated with ADHD. These factors were related to the hyperactive-impulsive and combined presentations, but they were not related to the inattentive presentation. Maternal weight gain was associated with subclinical ADHD. In conclusion, metabolic disorder in the pregnancy, difficulties in childbirth and specific family phenotype were related to ADHD, specifically with hyperactive-impulsive presentation, but not in subclinical ADHD.

Maternal antenatal depression and child mental health: Moderation by genomic risk for attention-deficit/hyperactivity disorder

Maternal antenatal depression strongly influences child mental health but with considerable inter-individual variation that is, in part, linked to genotype. The challenge is to effectively capture the genotypic influence. We outline a novel approach to describe genomic susceptibility to maternal antenatal depression focusing on child emotional/behavioral difficulties. Two cohorts provided measures of maternal depression, child genetic variation, and child mental health symptoms. We constructed a conventional polygenic risk score (PRS) for attention-deficit/hyperactivity disorder (ADHD) (PRSADHD) that significantly moderated the association between maternal antenatal depression and internalizing problems at 60 months (p = 2.94 × 10-4, R2 = .18). We then constructed an interaction PRS (xPRS) based on a subset of those single nucleotide polymorphisms from the PRSADHD that most accounted for the moderation of the association between maternal antenatal depression and child outcome. The interaction between maternal antenatal depression and this xPRS accounted for a larger proportion of the variance in child emotional/behavioral problems than models based on any PRSADHD (p = 5.50 × 10-9, R2 = .27), with similar findings in the replication cohort. The xPRS was significantly enriched for genes involved in neuronal development and synaptic function. Our study illustrates a novel approach to the study of genotypic moderation on the impact of maternal antenatal depression on child mental health and highlights the utility of the xPRS approach. These findings advance our understanding of individual differences in the developmental origins of mental health.

Pleiotropy and Cross-Disorder Genetics Among Psychiatric Disorders

Genome-wide analyses of common and rare genetic variations have documented the heritability of major psychiatric disorders, established their highly polygenic genetic architecture, and identified hundreds of contributing variants. In recent years, these studies have illuminated another key feature of the genetic basis of psychiatric disorders: the important role and pervasive nature of pleiotropy. It is now clear that a substantial fraction of genetic influences on psychopathology transcend clinical diagnostic boundaries. In this review, we summarize evidence in psychiatry for pleiotropy at multiple levels of analysis: from overall genome-wide correlation to biological pathways and down to the level of individual loci. We examine underlying mechanisms of observed pleiotropy, including genetic effects on neurodevelopment, diverse actions of regulatory elements, mediated effects, and spurious associations of genomic variation with multiple phenotypes. We conclude with an exploration of the implications of pleiotropy for understanding the genetic basis of psychiatric disorders, informing nosology, and advancing the aims of precision psychiatry and genomic medicine.

The positive end of the polygenic score distribution for ADHD: a low risk or a protective factor?

BACKGROUND

Polygenic scores (PGS) are widely used to characterize genetic liability for heritable mental disorders, including attention-deficit/hyperactivity disorder (ADHD). However, little is known about the effects of a low burden of genetic liability for ADHD, including whether this functions as a low risk or protective factor for ADHD and related functional outcomes in later life. The current study examines the association of low ADHD PGS and functional outcomes in adulthood.

METHODS

Participants were from Wave IV of the National Longitudinal Study of Adolescent to Adult Health (Add Health) (N = 7088; mean age = 29, s.d. = 1.74). ADHD PGS was computed from an existing genome-wide association study, and adult functional outcomes, including cognition, educational attainment, mental health, and physical health were assessed during in-home interviews.

RESULTS

Individuals at the lowest end of the ADHD PGS distribution (i.e. lowest 20th percentile) had the lowest probabilities of ADHD, exhibiting a 17-19% reduction in risk for ADHD relative to the observed 8.3% prevalence rate of ADHD in Add Health. Furthermore, individuals with low ADHD PGS had higher cognitive performance, greater levels of educational attainment, and lower BMI relative to individuals representing the rest of the ADHD PGS distribution, including those who were in the medium and high-PGS groups.

CONCLUSIONS

Findings indicate that psychiatric PGS likely capture far more than just the risk and the absence of risk for a psychiatric outcome; where one lies along the PGS distribution may predict diverging functional consequences, for better and for worse.

Creativity and ADHD: A review of behavioral studies, the effect of psychostimulants and neural underpinnings

Attention deficit/hyperactivity disorder (ADHD) is a debilitating disorder and most research therefore focuses on its deficits and its treatment. Research on the potential positive sides of ADHD is limited, and although a comprehensive overview of empirical studies on this subject is missing, it has been suggested that ADHD is associated with enhanced creativity. To identify important relations, trends and gaps in the literature, we review 31 behavioral studies on creativity and ADHD, distinguishing different research designs, age groups, creativity measurements and effects of psychostimulants, as well as reflecting the potential underlying neural mechanisms of creativity and ADHD. Most studies find evidence for increased divergent thinking for those with high ADHD scores (subclinical) but not for those with the disorder (clinical). The rates of creative abilities/achievements were high among both clinical and subclinical groups. We found no evidence for increased convergent thinking abilities in ADHD, nor did we find an overall negative effect of psychostimulants on creativity. Neuroscientific findings suggest candidate regions as well as mechanisms that should be studied further to increase our understanding of the relationship between creativity and ADHD. We propose research opportunities to boost the knowledge needed to better understand the potential positive side of ADHD.

Translating Discoveries in Attention-Deficit/Hyperactivity Disorder Genomics to an Outpatient Child and Adolescent Psychiatric Cohort

OBJECTIVE

Genomic discoveries should be investigated in generalizable child psychiatric samples in order to justify and inform studies that will evaluate their use for specific clinical purposes. In youth consecutively referred for neuropsychiatric evaluation, we examined 1) the convergent and discriminant validity of attention-deficit/hyperactivity disorder (ADHD) polygenic risk scores (PRSs) in relation to DSM-based ADHD phenotypes; 2) the association of ADHD PRSs with phenotypes beyond ADHD that share its liability and have implications for outcome; and 3) the extent to which youth with high ADHD PRSs manifest a distinctive clinical profile.

METHOD

Participants were 433 youth, ages 7-18 years, from the Longitudinal Study of Genetic Influences on Cognition. We used logistic/linear regression and mixed effects models to examine associations with ADHD-related polygenic variation from the largest ADHD genome-wide association study to date. We replicated key findings in 5,140 adult patients from a local health system biobank.

RESULTS

Among referred youth, ADHD PRSs were associated with ADHD diagnoses, cross-diagnostic ADHD symptoms and academic impairment (odds ratios ∼1.4; R² values ∼2%-3%), as well as cross-diagnostic variation in aggression and working memory. In adults, ADHD PRSs were associated with ADHD and phenotypes beyond the condition that have public health implications. Finally, youth with a high ADHD polygenic burden showed a more severe clinical profile than youth with a low burden (β coefficients ∼.2).

CONCLUSION

Among child and adolescent outpatients, ADHD polygenic risk was associated with ADHD and related phenotypes as well as clinical severity. These results extend the scientific foundation for studies of ADHD polygenic risk in the clinical setting and highlight directions for further research.

Transdiagnostic subtyping of males with developmental disorders using cortical characteristics

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Overlapping diagnosis and within-diagnosis heterogeneity was often reported in ASD.

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ASD and ADHD were subtyped regardless of diagnosis using cortical characteristics.

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The analysis revealed the number of subtypes as two.

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The boundary of the subtypes did not match the diagnostic boundary.

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The membership of subtypes was robust against the choice of an atlas.

Background

Autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) are biologically heterogeneous and often co-occur. As within-diagnosis heterogeneity and overlapping diagnoses are challenging for researchers and clinicians, identifying biologically homogenous subgroups, independent of diagnosis, is an urgent need.

Methods

MRI data from 148 adult males with developmental disorders (99 primary ASD, mean age = 31.7 ± 8.0, 49 primary ADHD; mean age = 31.7 ± 9.6) and 105 neurotypical controls (NTC; mean age = 30.6 ± 6.8) were analyzed. We extracted mean cortical thickness (CT) and surface area (SA) values using a functional atlas. Then, we conducted HeterogeneitY through DiscRiminant Analysis (HYDRA) to transdiagnostically cluster and classify individuals. Differences in diagnostic likelihood and clinical symptoms between subtypes were tested. Sensitivity analyses tested the stability of the number of subtypes and their membership by excluding 13 participants diagnosed with both ASD and ADHD and by using a different atlas.

Results

In relation to both CT and SA, HYDRA identified two subtypes. The likelihood of ASD or ADHD was not significantly different from the chance of belonging to any of these two subtypes. Clinical characteristics did not differ between subtypes in either CT or SA based analyses. The high consistency in membership was replicated when utilizing a different atlas or excluding people with dual diagnoses in CT (dice coefficients > 0.94) and in SA (>0.88).

Conclusion

Although the brain-derived subtypes do not match diagnostic groups, individuals with developmental disorders were successfully and stably subtyped using either CT or SA.

Polygenic Risk Score-Derived Subcortical Connectivity Mediates Attention-Deficit/Hyperactivity Disorder Diagnosis

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) has substantial heritability, and a recent large-scale investigation has identified common genome-wide significant loci associated with increased risk for ADHD. Along the same lines, many studies using noninvasive neuroimaging have identified differences in brain functional connectivity in children with ADHD. We attempted to bridge these studies to identify differences in functional connectivity associated with common genetic risk for ADHD using polygenic risk score (PRS).

METHODS

We computed ADHD PRSs for all participants in our sample (N = 315, children 7-13 years of age, 196 with ADHD and 119 unaffected comparison children) using ADHD data from the Psychiatric Genomics Consortium as a discovery set. Magnetic resonance imaging was used to evaluate resting-state functional connectivity of targeted subcortical structures.

RESULTS

The functional connectivity between 2 region pairs demonstrated a significant correlation to PRS: right caudate-parietal cortex and nucleus accumbens-occipital cortex. Connectivity between these areas, in addition to being correlated with PRS, was correlated with ADHD status. The connection between the caudate and the parietal region acted as a statistical suppressor, such that when it was included in a path model, the association between PRS and ADHD status was enhanced.

CONCLUSIONS

Our results suggest that functional connectivity to certain subcortical brain regions is directly altered by genetic variants, and certain cortico-subcortical connections may modulate ADHD-related genetic effects.

Polygenic risk scores for Alzheimer's disease, and academic achievement, cognitive and behavioural measures in children from the general population

OBJECTIVE

Several studies report a polygenic component of risk for Alzheimer's disease. Understanding whether this polygenic signal is associated with educational, cognitive and behavioural outcomes in children could provide an earlier window for intervention.

METHODS

We examined whether polygenic risk scores (PRS) at varying P-value thresholds in children from the Avon Longitudinal Study of Parents and Children were associated with academic achievement, cognitive and behavioural measures in childhood and adolescence.

RESULTS

We did not detect any evidence that the genome-wide significant PRS (5x10-8) were associated with these outcomes. PRS at the highest P-value threshold examined (P ≤ 5x10-1) were associated with lower academic achievement in adolescents (Key Stage 3; β: -0.03; 95% confidence interval: -0.05, -0.003) but the effect was attenuated when single nucleotide polymorphisms (SNPs) associated with educational attainment were removed. These PRS were associated with lower IQ (β: -0.04; 95% CI: -0.07, -0.02) at age 8 years with the effect remaining after removing SNPs associated with educational attainment.

CONCLUSIONS

SNPs mediating the biological effects of Alzheimer's disease are unlikely to operate early in life. The evidence of association between PRS for Alzheimer's disease at liberal thresholds and cognitive measures suggest shared genetic pathways between Alzheimer's disease, academic achievement and cognition.

ADHD symptoms in the adult general population are associated with factors linked to ADHD in adult patients

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder in children and adults. It is characterized by inappropriate levels of inattention (IA) and/or hyperactivity and impulsivity (HI). The ADHD diagnosis is hypothesized to represent the extreme of a continuous distribution of ADHD symptoms in the general population. In this study, we investigated whether factors linked to adult ADHD as a disorder are associated with adult ADHD symptoms in the general population. Our population-based sample included 4987 adults (mean age 56.1 years; 53.8% female) recruited by the Nijmegen Biomedical Study (NBS). Participants completed the Dutch ADHD DSM-IV Rating Scale for current and childhood ADHD symptoms, the Symptom Check List-90-R (SCL-90-R) anxiety subscale, and the Eysenk Personality Questionnaire (EPQR-S). Partial Spearman correlation and Hurdle negative binomial regression analysis were used to assess how age, sex, childhood ADHD symptoms, anxiety symptoms, and personality traits (neuroticism, extraversion, and psychoticism) are associated with current IA and HI symptoms. Increasing age was associated with a lower proportion of participants reporting HI symptoms and with reduced levels of HI; IA levels remained fairly stable over the age-range, but the probability of reporting IA symptoms increased throughout middle/late adulthood. Females were more likely to report IA symptoms than males. Childhood ADHD symptoms, neuroticism, and psychoticism were positively associated with current IA and HI symptoms, while extraversion had an opposite association with these symptom domains. Anxiety symptoms affected HI symptoms in females. Our results indicate that factors associated with categorical ADHD are also correlated with ADHD symptoms in the adult population.

SWAN scale for ADHD trait-based genetic research: a validity and polygenic risk study

BACKGROUND

Population-based samples with valid, quantitative and genetically informative trait measures of psychopathology could be a powerful complement to case/control genetic designs. We report the convergent and predictive validity of the parent- and self-report versions of the Strengths and Weaknesses of ADHD Symptoms and Normal Behavior Rating Scale (SWAN). We tested if SWAN scores were associated with ADHD diagnosis, ADHD polygenic risk, as well as traits and polygenic risk for disorders that co-occur with ADHD: anxiety and obsessive-compulsive disorder (OCD).

METHODS

We collected parent- and self-report SWAN scores in a sample of 15,560 children and adolescents (6-17 years) recruited at a science museum (Spit for Science sample). We established age and sex norms for the SWAN. Sensitivity-specificity analyses determined SWAN cut-points that discriminated those with and without a reported ADHD diagnosis. These cut-points were validated in a clinic sample (266 ADHD cases; 36 controls). Convergent validity was established using the Conners' parent- and self-report scales. Using Spit for Science participants with genome-wide data (n = 5,154), we tested if low, medium and high SWAN scores were associated with polygenic risk for ADHD, OCD and anxiety disorders.

RESULTS

Parent- and self-report SWAN scores showed high convergent validity with Conners' scales and distinguished ADHD participants with high sensitivity and specificity in the Spit for Science sample. In a clinic sample, the Spit for Science cut-points discriminated ADHD cases from controls with a sensitivity of 84% and specificity of 92%. High SWAN scores and scores above the Spit for Science cut-points were significantly associated with polygenic risk for ADHD. SWAN scores were not associated with polygenic risk for OCD or anxiety disorders.

CONCLUSIONS

Our study supports the validity of the parent- and self-report SWAN scales and their potential in ADHD population-based genetic research.

Genetics of attention deficit hyperactivity disorder

Decades of research show that genes play an vital role in the etiology of attention deficit hyperactivity disorder (ADHD) and its comorbidity with other disorders. Family, twin, and adoption studies show that ADHD runs in families. ADHD's high heritability of 74% motivated the search for ADHD susceptibility genes. Genetic linkage studies show that the effects of DNA risk variants on ADHD must, individually, be very small. Genome-wide association studies (GWAS) have implicated several genetic loci at the genome-wide level of statistical significance. These studies also show that about a third of ADHD's heritability is due to a polygenic component comprising many common variants each having small effects. From studies of copy number variants we have also learned that the rare insertions or deletions account for part of ADHD's heritability. These findings have implicated new biological pathways that may eventually have implications for treatment development.

Polygenic Risk Scores Derived From a Tourette Syndrome Genome-wide Association Study Predict Presence of Tics in the Avon Longitudinal Study of Parents and Children Cohort

BACKGROUND

Tourette syndrome (TS) has a well-established genetic background, but its genetic architecture remains largely unknown. The authors investigated the role of polygenic risk scores (PRSs) derived from a TS genome-wide association study in relation to the occurrence of tics and associated traits in a general population cohort.

METHODS

Using the most recent TS genome-wide association study (n = 4819 cases; n = 9488 controls) as the discovery sample, PRSs were calculated in Avon Longitudinal Study of Parents and Children participants (n = 8941). Regression analyses were used to assess whether PRS predicted the presence and chronicity of tics, and symptom severity of obsessive-compulsive disorder, attention-deficit/hyperactivity disorder, and autism spectrum disorder in Avon Longitudinal Study of Parents and Children participants.

RESULTS

Following correction for multiple testing, the PRS significantly predicted the presence (R2 = .48%, p empirical = .01, Q = .04) but not the chronicity (R2 = .16%, p empirical = .07, Q = .14) of tics in the Avon Longitudinal Study of Parents and Children cohort; it did not predict the severity of obsessive-compulsive disorder (R2 = .11%, p empirical = .11, Q = .15), attention-deficit/hyperactivity disorder (R2 = .09%, p empirical = .19, Q = .21), or autism spectrum disorder (R2 = .12%, p empirical = .09, Q = .14).

CONCLUSIONS

The authors found a significant polygenic component of tics occurring in a general population cohort based on PRS derived from a genome-wide association study of individuals with a TS diagnosis. This finding supports the notion that tics along a spectrum from nonclinical to clinical symptom levels share a similar genetic background.

Genetic and environmental aetiologies of associations between dispositional mindfulness and ADHD traits: a population-based twin study

To get additional insight into the phenotype of attentional problems, we examined to what extent genetic and environmental factors explain covariation between lack of dispositional mindfulness and attention-deficit/hyperactivity disorder (ADHD) traits in youth, and explored the incremental validity of these constructs in predicting life satisfaction. We used data from a UK population-representative sample of adolescent twins (N = 1092 pairs) on lack of dispositional mindfulness [Mindful Attention Awareness Scale (MAAS)], ADHD traits [Conners' Parent Rating Scale-Revised (CPRS-R): inattentive (INATT) and hyperactivity/impulsivity (HYP/IMP) symptom dimensions] and life satisfaction (Students' Life Satisfaction Scale). Twin model fitting analyses were conducted. Phenotypic correlations (r_p) between MAAS and CPRS-R (INATT: r_p = 0.18, HYP/IMP: r_p = 0.13) were small, but significant and largely explained by shared genes for INATT (% r_p INATT-MAAS due to genes: 93%, genetic correlation r_A = 0.37) and HYP/IMP (% r_p HYP/IMP-MAAS due to genes: 81%; genetic correlation r_A = 0.21) with no significant contribution of environmental factors. MAAS, INATT and HYP/IMP significantly and independently predicted life satisfaction. Lack of dispositional mindfulness, assessed as self-reported perceived lapses of attention (MAAS), taps into an aspect of attentional functioning that is phenotypically and genetically distinct from parent-rated ADHD traits. The clinically relevant incremental validity of both scales implicates that MAAS could be used to explore the underlying mechanisms of an aspect of attentional functioning that uniquely affects life satisfaction and is not captured by DSM-based ADHD scales. Further future research could identify if lack of dispositional mindfulness and high ADHD traits can be targeted by different therapeutic approaches resulting in different effects on life satisfaction.

Assessing the evidence for shared genetic risks across psychiatric disorders and traits

Genetic influences play a significant role in risk for psychiatric disorders, prompting numerous endeavors to further understand their underlying genetic architecture. In this paper, we summarize and review evidence from traditional twin studies and more recent genome-wide molecular genetic analyses regarding two important issues that have proven particularly informative for psychiatric genetic research. First, emerging results are beginning to suggest that genetic risk factors for some (but not all) clinically diagnosed psychiatric disorders or extreme manifestations of psychiatric traits in the population share genetic risks with quantitative variation in milder traits of the same disorder throughout the general population. Second, there is now evidence for substantial sharing of genetic risks across different psychiatric disorders. This extends to the level of characteristic traits throughout the population, with which some clinical disorders also share genetic risks. In this review, we summarize and evaluate the evidence for these two issues, for a range of psychiatric disorders. We then critically appraise putative interpretations regarding the potential meaning of genetic correlation across psychiatric phenotypes. We highlight several new methods and studies which are already using these insights into the genetic architecture of psychiatric disorders to gain additional understanding regarding the underlying biology of these disorders. We conclude by outlining opportunities for future research in this area.

Association of Polygenic Risk for Attention-Deficit/Hyperactivity Disorder With Co-occurring Traits and Disorders

BACKGROUND

A recent large-scale mega genome-wide association study identified, for the first time, genetic variants at 12 loci significantly associated with attention-deficit/hyperactivity disorder (ADHD). In this study we use a powerful polygenic approach, with polygenic scores derived from the genome-wide association study, to investigate the etiological overlap between ADHD and frequently co-occurring traits and disorders.

METHODS

Polygenic risk scores for ADHD derived from the mega genome-wide association study (20,183 cases and 35,191 control subjects) were computed in a large-scale adult population sample (N = 135,726) recruited by the UK Biobank. Regression analyses were conducted to investigate whether polygenic risk for ADHD is associated with related traits and disorders in this population sample. The effects of sex were investigated via inclusion of an interaction term in the models.

RESULTS

Polygenic risk for ADHD significantly and positively predicted body mass index (R2 = .45%; p = 5 × 10-129), neuroticism (R2 = .09%; p = 2 × 10-24), depression (R2 = .11%; p = 2 × 10-13), anxiety (R2 = .06%; p = 3 × 10-4), risk taking (R2 = .12%; p = 9 × 10-25), alcohol intake (R2 = .09%; p = 8 × 10-29), smoking (R2 = .33%; p = 4 × 10-21), alcohol dependency (R2 = .21%; p = 5 × 10-6), and negatively predicted verbal-numerical reasoning (R2 = .38%; p = 5 × 10-36). Polygenic risk scores did not significantly predict schizophrenia or bipolar disorder, although this may be because of the small number of diagnostic cases. We found no interaction effects between polygenic risk for ADHD and sex on any phenotypes.

CONCLUSIONS

Our findings suggest that common genetic variation underlying risk for clinically diagnosed ADHD also contributes to higher body mass index, neuroticism, anxiety and depressive disorders, alcohol and nicotine use, risk taking, and lower general cognitive ability in the general population. These findings suggest that the co-occurrence of several traits with ADHD is partly explained by the same common genetic variants.

Association of copy number variation across the genome with neuropsychiatric traits in the general population

Copy number variants (CNVs) are associated with psychiatric conditions in clinical populations. The relationship between rare CNV burden and neuropsychiatric traits in young, general populations is underexplored. A total of 6,807 children from the Avon Longitudinal Study of Parents and Children (ALSPAC) were studied. CNVs were inferred from single nucleotide polymorphism-array data using PennCNV. After excluding children with known candidate CNVs for schizophrenia (SCZ), rare (<1%) CNV burden (total number of genes affected by CNVs, total length of CNVs, and largest CNV carried) was analyzed in relation to: psychotic experiences (PEs) and anxiety/depression in adolescence; autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD), ASD and ADHD traits, and cognitive measures during childhood. Outcomes were also assessed in relation to known SCZ CNVs. The number of genes affected by rare CNVs was associated with a continuous measure of ASD: the standardized mean difference [SMD] per gene affected was increased by 0.018 [95%CI 0.011,0.025], p = 3e-07 for duplications and by 0.021 [95%CI 0.010, 0.032], p = 1e-04 for deletions. In line with our published results on educational attainment in ALSPAC, intelligence quotient (IQ) was associated with CNV burden: the SMD per gene affected was -0.017 [95%CI -0.025, -0.008] p = 1e-04 for duplications and -0.023 [95%CI -0.037, -0.009], p = .002 for deletions. Associations were also observed for measures of coherence, attention, memory, and social cognition. SCZ-associated deletions were associated with IQ (SMD: -0.617 [95%CI -0.936, -0.298], p = 2e-04), but not with PEs or other traits. We found that rare CNV burden and known SCZ candidate CNVs are associated with neuropsychiatric phenotypes in a nonclinically ascertained sample of young people.

Working Memory and Vigilance as Multivariate Endophenotypes Related to Common Genetic Risk for Attention-Deficit/Hyperactivity Disorder

OBJECTIVE

Understanding the role of endophenotypes is essential for process models of psychopathology. This study examined which candidate cognitive endophenotypes statistically mediate common variant genetic risk for attention-deficit/hyperactivity disorder (ADHD).

METHOD

A case-control design using community-recruited volunteer children 7 to 11 years of age (n = 656, n = 435 ADHD), of whom 514 were of homogenous European ancestry for the primary models (n = 337 ADHD, 177 non-ADHD). Children were assessed with a multi-informant, best-estimate diagnostic procedure and laboratory measures of working memory, response inhibition, executive functioning, arousal/attention, temporal information processing, and processing speed. Latent variables were created for the candidate cognitive measures and for parent- and teacher-rated ADHD dimensions. Polygenic risk scores (PGS) were computed using a discovery sample of 20,183 individuals with ADHD and 35,191 controls from the Psychiatric Genetics Consortium. Cognitive measures that survived multiple testing correction for association with the PGS were evaluated for mediation with ADHD using structural equation models.

RESULTS

Results were essentially identical in the homogeneous European ancestry subgroup (n = 514) and in the full sample (N = 656). For the European population, the PGS was associated with ADHD diagnosis (Nagelkerke R2 = 0.045; β = 0.233, SE = 0.053, p = .000011) and multi-indicator dimensional ADHD latent variables by parent report (β = 0.185, SE = 0.043) and teacher report (β = 0.165, SE = 0.042). The PGS effect was statistically mediated by working memory (indirect effect, β = 0.101, SE = 0.029, 95% CI = 0.05, 0.16, p = .00049, 43% of genetic effect accounted for) and arousal/alertness (indirect effect β = 0.115, 95% CI = 0.04, 0.20, SE = 0.041, p = .005, 49% of genetic effect accounted for).

CONCLUSION

This is the first clear demonstration from molecular genetic data that working memory and arousal regulation are promising cognitive endophenotypes for ADHD with regard to mediating genetic risk from common genetic variants.

Genetic Overlap Between Schizophrenia and Developmental Psychopathology: Longitudinal and Multivariate Polygenic Risk Prediction of Common Psychiatric Traits During Development

Background

Several nonpsychotic psychiatric disorders in childhood and adolescence can precede the onset of schizophrenia, but the etiology of this relationship remains unclear. We investigated to what extent the association between schizophrenia and psychiatric disorders in childhood is explained by correlated genetic risk factors.

Methods

Polygenic risk scores (PRS), reflecting an individual's genetic risk for schizophrenia, were constructed for 2588 children from the Netherlands Twin Register (NTR) and 6127 from the Avon Longitudinal Study of Parents And Children (ALSPAC). The associations between schizophrenia PRS and measures of anxiety, depression, attention deficit hyperactivity disorder (ADHD), and oppositional defiant disorder/conduct disorder (ODD/CD) were estimated at age 7, 10, 12/13, and 15 years in the 2 cohorts. Results were then meta-analyzed, and a meta-regression analysis was performed to test differences in effects sizes over, age and disorders.

Results

Schizophrenia PRS were associated with childhood and adolescent psychopathology. Meta-regression analysis showed differences in the associations over disorders, with the strongest association with childhood and adolescent depression and a weaker association for ODD/CD at age 7. The associations increased with age and this increase was steepest for ADHD and ODD/CD. Genetic correlations varied between 0.10 and 0.25.

Conclusion

By optimally using longitudinal data across diagnoses in a multivariate meta-analysis this study sheds light on the development of childhood disorders into severe adult psychiatric disorders. The results are consistent with a common genetic etiology of schizophrenia and developmental psychopathology as well as with a stronger shared genetic etiology between schizophrenia and adolescent onset psychopathology.

Y Chromosome, Mitochondrial DNA and Childhood Behavioural Traits

Many psychiatric traits are sexually dimorphic in terms of prevalence, age of onset, progression and prognosis; sex chromosomes could play a role in these differences. In this study we evaluated the association between Y chromosome and mitochondrial DNA haplogroups with sexually-dimorphic behavioural and psychiatric traits. The study sample included 4,211 males and 4,009 females with mitochondrial DNA haplogroups and 4,788 males with Y chromosome haplogroups who are part of the Avon Longitudinal Study of Parents and Children (ALSPAC) based in the United Kingdom. Different subsets of these populations were assessed using measures of behavioural and psychiatric traits with logistic regression being used to measure the association between haplogroups and the traits. The majority of behavioural traits in our cohort differed between males and females; however Y chromosome and mitochondrial DNA haplogroups were not associated with any of the variables. These findings suggest that if there is common variation on the Y chromosome and mitochondrial DNA associated with behavioural and psychiatric trait variation, it has a small effect.

Cdh13 and AdipoQ gene knockout alter instrumental and Pavlovian drug conditioning

Genome-wide association studies in humans have suggested that variants of the cadherin-13 (CDH13) gene are associated with substance use disorder, subjective response to amphetamine, and attention deficit hyperactivity disorder. To examine the role of the Cdh13 and its peptide ligand adiponectin (AdipoQ) in addiction-related behaviors, we assessed Cdh13 knockout (KO) rats and AdipoQ KO mice using intravenous cocaine self-administration and conditioned place preference (CPP) paradigms. During intravenous cocaine self-administration, male Cdh13 heterozygous (+/-) and KO (-/-) rats showed increased cue-induced reinstatement compared with wild-type (WT) rats when presented with a cocaine-paired stimulus, whereas female Cdh13 rats showed no differences across genotype. Cdh13 -/- rats showed higher responding for a saccharin reinforcer and learned the choice reaction time (RT) task more slowly than WTs. However, we found no differences between Cdh13 -/- and +/+ rats in responding for sensory reinforcement, number of premature responses in the RT task, tendency to approach a Pavlovian food cue, CPP and locomotor activation to cocaine (10 or 20 mg/kg). In AdipoQ -/- mice, there was a significant increase in CPP to methamphetamine (1 mg/kg) but not to a range of d-amphetamine doses (0.5, 1, 2 and 4 mg/kg). Taken together, these data suggest that Cdh13 and AdipoQ regulate sensitivity to psychomotor stimulants and palatable rewards without producing major changes in other behaviors. In humans, these two genes may regulate sensitivity to natural and drug rewards, thus influencing susceptibility to the conditioned drug effects and relapse.

Genetic and psychosocial predictors of alcohol use trajectories among disaster-exposed adolescents

BACKGROUND AND OBJECTIVES

Adolescent alcohol misuse is associated with numerous long-term adverse outcomes, so we examined predictors of alcohol use among disaster-exposed adolescents, a group at-risk for alcohol misuse.

METHODS

The current study (n = 332) examined severity of tornado-related exposure, posttraumatic stress disorder (PTSD) symptoms, emotional support, and a genetic risk sum score (GRSS) as predictors of alcohol use trajectories.

RESULTS

Severity of exposure interacted with the GRSS to predict both intercept (12-month follow up quantity of alcohol use) and growth rate. Emotional support also interacted with adolescent PTSD symptoms to predict intercept and growth rate.

DISCUSSION AND CONCLUSIONS

Adolescents with greater severity of disaster exposure and high genetic risk comprise a high risk group, on which efforts to prevent alcohol use should be focused. Additionally, emotional support is essential in buffering the effects of PTSD symptoms on alcohol use outcomes among adolescents.

SCIENTIFIC SIGNIFICANCE

Toward the aim of reducing adolescent alcohol misuse following disaster exposure, there is utility in inserting immediate supports (e.g., basic resources) into communities/families that have experienced significant disaster-related severity, particularly among adolescents at high levels of genetic risk for alcohol use/misuse. Additionally, prevention efforts aimed at improving emotional supports for adolescents with more PTSD symptoms may reduce propensity for alcohol misuse following disaster. This information can be easily incorporated into existing web-based interventions. (Am J Addict 2017;26:623-631).

Shared genetic influences between dimensional ASD and ADHD symptoms during child and adolescent development

BACKGROUND

Shared genetic influences between attention-deficit/hyperactivity disorder (ADHD) symptoms and autism spectrum disorder (ASD) symptoms have been reported. Cross-trait genetic relationships are, however, subject to dynamic changes during development. We investigated the continuity of genetic overlap between ASD and ADHD symptoms in a general population sample during childhood and adolescence. We also studied uni- and cross-dimensional trait-disorder links with respect to genetic ADHD and ASD risk.

METHODS

Social-communication difficulties (N ≤ 5551, Social and Communication Disorders Checklist, SCDC) and combined hyperactive-impulsive/inattentive ADHD symptoms (N ≤ 5678, Strengths and Difficulties Questionnaire, SDQ-ADHD) were repeatedly measured in a UK birth cohort (ALSPAC, age 7 to 17 years). Genome-wide summary statistics on clinical ASD (5305 cases; 5305 pseudo-controls) and ADHD (4163 cases; 12,040 controls/pseudo-controls) were available from the Psychiatric Genomics Consortium. Genetic trait variances and genetic overlap between phenotypes were estimated using genome-wide data.

RESULTS

In the general population, genetic influences for SCDC and SDQ-ADHD scores were shared throughout development. Genetic correlations across traits reached a similar strength and magnitude (cross-trait rg ≤ 1, pmin  = 3 × 10-4) as those between repeated measures of the same trait (within-trait rg ≤ 0.94, pmin  = 7 × 10-4). Shared genetic influences between traits, especially during later adolescence, may implicate variants in K-RAS signalling upregulated genes (p-meta = 6.4 × 10-4). Uni-dimensionally, each population-based trait mapped to the expected behavioural continuum: risk-increasing alleles for clinical ADHD were persistently associated with SDQ-ADHD scores throughout development (marginal regression R2 = 0.084%). An age-specific genetic overlap between clinical ASD and social-communication difficulties during childhood was also shown, as per previous reports. Cross-dimensionally, however, neither SCDC nor SDQ-ADHD scores were linked to genetic risk for disorder.

CONCLUSIONS

In the general population, genetic aetiologies between social-communication difficulties and ADHD symptoms are shared throughout child and adolescent development and may implicate similar biological pathways that co-vary during development. Within both the ASD and the ADHD dimension, population-based traits are also linked to clinical disorder, although much larger clinical discovery samples are required to reliably detect cross-dimensional trait-disorder relationships.

Future Directions for Work on Refinement of ADHD Assessment in Young Adults

Sibley, Coxe, and Molina provide a thoughtful discussion of the implications of our study and highlight important future directions in this line of work. They helpfully amplify several themes that space did not allow discussion of in our article. In particular, they correctly emphasize the importance of theoretical as well as statistical considerations in model selection. We also agree that clinical tests of sensitivity and specificity, taking into account different base rates and types of samples, are essential before a final algorithm would be ready for dissemination. However, we are not convinced that such tests should be limited to populations of individuals with attention-deficit/hyperactivity disorder (ADHD). Rather, they should include those with and without diagnosed ADHD in order to provide comprehensive tests of reporter sensitivity and specificity across the entire continuum of ADHD symptomatology and in relation to different populations, including other disorders and typically developing populations.

Association between polygenic risk scores for attention-deficit hyperactivity disorder and educational and cognitive outcomes in the general population

Background

Children with a diagnosis of attention-deficit hyperactivity disorder ADHD) have lower cognitive ability and are at risk of adverse educational outcomes; ADHD genetic risks have been found to predict childhood cognitive ability and other neurodevelopmental traits in the general population; thus genetic risks might plausibly also contribute to cognitive ability later in development and to educational underachievement.

Methods

We generated ADHD polygenic risk scores in the Avon Longitudinal Study of Parents and Children participants (maximum N : 6928 children and 7280 mothers) based on the results of a discovery clinical sample, a genome-wide association study of 727 cases with ADHD diagnosis and 5081 controls. We tested if ADHD polygenic risk scores were associated with educational outcomes and IQ in adolescents and their mothers.

Results

High ADHD polygenic scores in adolescents were associated with worse educational outcomes at Key Stage 3 [national tests conducted at age 13-14 years; β = -1.4 (-2.0 to -0.8), P  = 2.3 × 10 -6 ), at General Certificate of Secondary Education exams at age 15-16 years (β = -4.0 (-6.1 to -1.9), P  = 1.8 × 10 -4 ], reduced odds of sitting Key Stage 5 examinations at age 16-18 years [odds ratio (OR) = 0.90 (0.88 to 0.97), P  = 0.001] and lower IQ scores at age 15.5 [β = -0.8 (-1.2 to -0.4), P  = 2.4 × 10 -4 ]. Moreover, maternal ADHD polygenic scores were associated with lower maternal educational achievement [β = -0.09 (-0.10 to -0.06), P  = 0.005] and lower maternal IQ [β = -0.6 (-1.2 to -0.1), P  = 0.03].

Conclusions

ADHD diagnosis risk alleles impact on functional outcomes in two generations (mother and child) and likely have intergenerational environmental effects.

Neurodevelopmental disorders

Neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder, although most commonly considered in childhood, can be lifelong conditions. In this Personal View that is shaped by clinical experience and research, we adopt a conceptual approach. First, we discuss what disorders are neurodevelopmental and why such a grouping is useful. We conclude that both distinction and grouping are helpful and that it is important to take into account the strong overlap across neurodevelopmental disorders. Then we highlight some challenges in bridging research and clinical practice. We discuss the complexity of clinical phenotypes and the importance of the social context. We also argue the importance of viewing neurodevelopmental disorders as traits but highlight that this is not the only approach to use. Finally, we consider developmental change across the life-span. Overall, we argue strongly for a flexible approach in clinical practice that takes into consideration the high level of heterogeneity and overlap in neurodevelopmental disorders and for research to link more closely to what is observed in real-life practice.

Polygenic risk for five psychiatric disorders and cross-disorder and disorder-specific neural connectivity in two independent populations

Major psychiatric disorders, including attention deficit hyperactivity disorder (ADHD), autism (AUT), bipolar disorder (BD), major depressive disorder (MDD), and schizophrenia (SZ), are highly heritable and polygenic. Evidence suggests that these five disorders have both shared and distinct genetic risks and neural connectivity abnormalities. To measure aggregate genetic risks, the polygenic risk score (PGRS) was computed. Two independent general populations (N = 360 and N = 323) were separately examined to investigate whether the cross-disorder PGRS and PGRS for a specific disorder were associated with individual variability in functional connectivity. Consistent altered functional connectivity was found with the bilateral insula: for the left supplementary motor area and the left superior temporal gyrus with the cross-disorder PGRS, for the left insula and right middle and superior temporal lobe associated with the PGRS for autism, for the bilateral midbrain, posterior cingulate, cuneus, and precuneus associated with the PGRS for BD, and for the left angular gyrus and the left dorsolateral prefrontal cortex associated with the PGRS for schizophrenia. No significant functional connectivity was found associated with the PGRS for ADHD and MDD. Our findings indicated that genetic effects on the cross-disorder and disorder-specific neural connectivity of common genetic risk loci are detectable in the general population. Our findings also indicated that polygenic risk contributes to the main neurobiological phenotypes of psychiatric disorders and that identifying cross-disorder and specific functional connectivity related to polygenic risks may elucidate the neural pathways for these disorders.

•

Altered cross-disorder functional connectivity related to PGRSs is detected.

•

Altered disorder-specific functional connectivity related to PGRSs is detected.

•

Altered functional connectivity related to PGRSs is involved in brain networks.

•

Polygenic risk contributes to neurobiological phenotypes of psychiatric disorders.

Childhood hyperactivity and mood problems at mid-life: evidence from a prospective birth cohort

PURPOSE

Childhood hyperactivity leads to mental health problems, but it is not known whether there are long-term risks for adult mood problems in unselected population cohorts that extend to mid-life. Aims were to examine links between childhood hyperactivity and mood problems up to age 50 years and to consider confounding factors and gender differences in associations.

METHODS

The National Child Development Study (NCDS) is a UK cohort of children born in 1958. Children with (N = 453) and without (N = 9192) pervasive and persistent hyperactivity were followed to age 50. Adult mood was assessed using the Malaise Inventory at ages 23, 33, 42, and 50 years and the CIS-R interview at 45 years.

RESULTS

Childhood hyperactivity predicted low mood at all adult assessments (ES = 0.27-0.45), including after covariate adjustment (childhood adversity, emotional and behavioural problems, and attainment).

CONCLUSION

Hyperactivity has enduring risk effects on low mood throughout the life course that extend to middle age.

GAD1 gene polymorphisms are associated with hyperactivity in Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is one of the most common neurodevelopmental disorders of childhood. Recent studies suggest a role for γ-aminobutyric acid (GABA) on ADHD hyperactive/impulsive symptoms due to behavioral disinhibition resulting from inappropriate modulation of both glutamatergic and GABAergic signaling. The glutamic acid decarboxylase (GAD1) gene encodes a key enzyme of GABA biosynthesis. The aim of the present study was to investigate the possible influence of GAD1 SNPs rs3749034 and rs11542313 on ADHD susceptibility. The clinical sample consisted of 547 families with ADHD probands recruited at the ADHD Outpatient Clinics from Hospital de Clínicas de Porto Alegre. Hyperactive/impulsive symptoms were evaluated based on parent reports from the Swanson, Nolan, and Pelham Scale-version IV (SNAP-IV). The C allele of rs11542313 was significantly overtransmitted from parents to ADHD probands (P = 0.02). Hyperactive/impulsive score was higher in rs3749034G allele (P = 0.005, Cohen's D = 0.19) and rs11542313C allele (P = 0.03; Cohen's D = 0.16) carriers. GAD1 haplotypes were also associated with higher hyperactive/impulsive scores in ADHD youths (global P-value = 0.01). In the specific haplotype test, the GC haplotype was the one with the highest hyperactive/impulsive scores (P = 0.03). Our results suggest that the GAD1 gene is associated with ADHD susceptibility, contributing particularly to the hyperactive/impulsive symptom domain. © 2016 Wiley Periodicals, Inc.

Understanding attention deficit hyperactivity disorder as a continuum

OBJECTIVE

To review research findings that consider whether attention deficit hyperactivity disorder (ADHD) is a discrete entity or whether it is more consistent with an extreme end-of-trait distribution in the population and to then grapple with the potential clinical implications.

QUALITY OF EVIDENCE

Peer-reviewed publications in the past 5 years, drawing from diverse fields (taxonomy, epidemiology, genetics, neurobiology, and neuropsychology), were identified through searches in MEDLINE and PsycINFO.

MAIN MESSAGE

Accumulating research findings are most consistent with a predominately dimensional rather than a qualitatively distinct existence for ADHD. This does not negate the clinical needs of those who have substantial ADHD symptom clusters, nor the risks that such symptoms entail. However, the lack of discontinuity in the distribution of such traits in the population creates great uncertainty as to what thresholds should prompt explicit intervention.

CONCLUSION

The implications of this pattern of findings might include the need to de-emphasize categorical conceptualizations of ADHD, produce evidence to better inform risk-benefit ratios of interventions along a spectrum of symptom and functional severity, and more coherently triage and arrange service delivery on the basis of symptom and functional severity rather than artificial diagnostic categorizations.

COMT and DAT1 genes are associated with hyperactivity and inattention traits in the 1993 Pelotas Birth Cohort: evidence of sex-specific combined effect

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) symptoms are dimensionally distributed in the population. This study aimed to assess the role of the catechol-O-methyltransferase (COMT) and of the dopamine transporter (DAT1) genes on ADHD symptoms in the general population.

METHODS

We investigated 4101 individuals from the 1993 Pelotas Birth Cohort Study using the parent version of the Strengths and Difficulties Questionnaire (SDQ) at ages 11 and 15 years. The SDQ hyperactivity/inattention scores were the main outcomes.

RESULTS

Linear regression analyses demonstrated that the increasing number of COMT158Val and DAT1 10R alleles significantly predicted increasing SDQ hyperactivity/inattention scores in boys at both 11 and 15 years of age (β coefficient = 0.049, t = 2.189, p = 0.029, R² = 0.012, and β coefficient = 0.064, t = 2.832, p = 0.005, R² = 0.008, respectively). The presence of both COMT158Val and DAT1 10R alleles was also associated with full categorical ADHD diagnosis at 18 years of age in boys (χ² = 4.561, p = 0.033, odds ratio 2.473, 95% confidence interval 1.048-5.838) from this cohort. We did not observe these associations in girls.

LIMITATIONS

Our analyses of SDQ hyperactivity/inattention scores were not corrected for SDQ scores of conduct problems because these variables were highly correlated.

CONCLUSION

This study demonstrates a role for COMT and DAT1 genes on hyperactivity/inattention symptoms and provides further support for ADHD as the extreme of traits that vary in the population. It also confirms previous evidence for sexual dimorphism on COMT and DAT1 gene expression.

A Genome-Wide Association Meta-Analysis of Attention-Deficit/Hyperactivity Disorder Symptoms in Population-Based Pediatric Cohorts

OBJECTIVE

The aims of this study were to elucidate the influence of common genetic variants on childhood attention-deficit/hyperactivity disorder (ADHD) symptoms, to identify genetic variants that explain its high heritability, and to investigate the genetic overlap of ADHD symptom scores with ADHD diagnosis.

METHOD

Within the EArly Genetics and Lifecourse Epidemiology (EAGLE) consortium, genome-wide single nucleotide polymorphisms (SNPs) and ADHD symptom scores were available for 17,666 children (<13 years of age) from nine population-based cohorts. SNP-based heritability was estimated in data from the three largest cohorts. Meta-analysis based on genome-wide association (GWA) analyses with SNPs was followed by gene-based association tests, and the overlap in results with a meta-analysis in the Psychiatric Genomics Consortium (PGC) case-control ADHD study was investigated.

RESULTS

SNP-based heritability ranged from 5% to 34%, indicating that variation in common genetic variants influences ADHD symptom scores. The meta-analysis did not detect genome-wide significant SNPs, but three genes, lying close to each other with SNPs in high linkage disequilibrium (LD), showed a gene-wide significant association (p values between 1.46 × 10(-6) and 2.66 × 10(-6)). One gene, WASL, is involved in neuronal development. Both SNP- and gene-based analyses indicated overlap with the PGC meta-analysis results with the genetic correlation estimated at 0.96.

CONCLUSION

The SNP-based heritability for ADHD symptom scores indicates a polygenic architecture, and genes involved in neurite outgrowth are possibly involved. Continuous and dichotomous measures of ADHD appear to assess a genetically common phenotype. A next step is to combine data from population-based and case-control cohorts in genetic association studies to increase sample size and to improve statistical power for identifying genetic variants.

Association of Acetaminophen Use During Pregnancy With Behavioral Problems in Childhood: Evidence Against Confounding

IMPORTANCE

Acetaminophen (paracetamol) is used by a large proportion of pregnant women. Research suggests that acetaminophen use in pregnancy is associated with abnormal fetal neurodevelopment. However, it is possible that this association might be confounded by unmeasured behavioral factors linked to acetaminophen use.

OBJECTIVE

To examine associations between offspring behavioral problems and (1) maternal prenatal acetaminophen use, (2) maternal postnatal acetaminophen use, and (3) partner's acetaminophen use.

DESIGN, SETTING, AND PARTICIPANTS

From February 2015 to March 2016, we collected and analyzed data from the Avon Longitudinal Study of Parents and Children (ALSPAC), a prospective birth cohort. We studied 7796 mothers enrolled in ALSPAC between 1991 and 1992 along with their children and partners.

EXPOSURES

Acetaminophen use was assessed by questionnaire completion at 18 and 32 weeks of pregnancy and when the child was 61 months old.

MAIN OUTCOMES AND MEASURES

Maternal reports of behavioral problems using the Strengths and Difficulties Questionnaire (SDQ) when the children were 7 years old. We estimated risk ratios for behavioral problems in children after prenatal, postnatal, and partner's exposure to acetaminophen and mutually adjusted each association.

RESULTS

Maternal prenatal acetaminophen use at 18 (n = 4415; 53%) and 32 weeks of pregnancy (n = 3381; 42%) was associated with higher odds of having conduct problems (risk ratio [RR], 1.42; 95% CI, 1.25-1.62) and hyperactivity symptoms (RR, 1.31; 95% CI, 1.16-1.49), while maternal acetaminophen use at 32 weeks was also associated with higher odds of having emotional symptoms (RR, 1.29; 95% CI, 1.09-1.53) and total difficulties (RR, 1.46; 95% CI, 1.21-1.77). This was not the case for maternal postnatal (n = 6916; 89%) or partner's (n = 3454; 84%) acetaminophen use. We found the associations between maternal prenatal acetaminophen use and all the SDQ domains unchanged even after adjusting for maternal postnatal or partner's acetaminophen use.

CONCLUSIONS AND RELEVANCE

Children exposed to acetaminophen prenatally are at increased risk of multiple behavioral difficulties, and the associations do not appear to be explained by unmeasured behavioral or social factors linked to acetaminophen use insofar as they are not observed for postnatal or partner's acetaminophen use. Although these results could have implications for public health advice, further studies are required to replicate the findings and to understand mechanisms.