Contrast Effects and Sex Influence Maternal and Self-Report Dimensional Measures of Attention-Deficit Hyperactivity Disorder

Etiology of the Broad Avoidant Restrictive Food Intake Disorder Phenotype in Swedish Twins Aged 6 to 12 Years

Importance

Avoidant restrictive food intake disorder (ARFID) is characterized by an extremely limited range and/or amount of food eaten, resulting in the persistent failure to meet nutritional and/or energy needs. Its etiology is poorly understood, and knowledge of genetic and environmental contributions to ARFID is needed to guide future research.

Objective

To estimate the extent to which genetic and environmental factors contribute to the liability to the broad ARFID phenotype.

Design, Setting, and Participants

This nationwide Swedish twin study includes 16 951 twin pairs born between 1992 and 2010 whose parents participated in the Child and Adolescent Twin Study in Sweden (CATSS) at twin age 9 or 12 years. CATSS was linked to the National Patient Register (NPR) and the Prescribed Drug Register (PDR). Data were collected from July 2004 to April 2020, and data were analyzed from October 2021 to October 2022.

Main Outcomes and Measures

From CATSS, NPR, and PDR, all parent reports, diagnoses, procedures, and prescribed drugs that were relevant to the DSM-5 ARFID criteria were extracted when twin pairs were aged 6 to 12 years and integrated into a composite measure for the ARFID phenotype (ie, avoidant/restrictive eating with clinically significant impact, such as low weight or nutritional deficiency, and with fear of weight gain as an exclusion). In sensitivity analyses, autism and medical conditions that could account for the eating disturbance were controlled for. Univariate liability threshold models were fitted to estimate the relative contribution of genetic and environmental variation to the liability to the ARFID phenotype.

Results

Of 33 902 included children, 17 151 (50.6%) were male. A total of 682 children (2.0%) with the ARFID phenotype were identified. The heritability of ARFID was 0.79 (95% CI, 0.70-0.85), with significant contributions from nonshared environmental factors (0.21; 95% CI, 0.15-0.30). Heritability was very similar when excluding children with autism (0.77; 95% CI, 0.67-0.84) or medical illnesses that could account for the eating disturbance (0.79; 95% CI, 0.70-0.86).

Conclusions and Relevance

Prevalence and sex distribution of the broad ARFID phenotype were similar to previous studies, supporting the use of existing epidemiological data to identify children with ARFID. This study of the estimated genetic and environmental etiology of ARFID suggests that ARFID is highly heritable, encouraging future twin and molecular genetic studies.

Insights into attention-deficit/hyperactivity disorder from recent genetic studies

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable neurodevelopmental disorder (NDD). In this narrative review, we summarize recent advances in quantitative and molecular genetic research from the past 5-10 years. Combined with large-scale international collaboration, these advances have resulted in fast-paced progress in understanding the etiology of ADHD and how genetic risk factors map on to clinical heterogeneity. Studies are converging on a number of key insights. First, ADHD is a highly polygenic NDD with a complex genetic architecture encompassing risk variants across the spectrum of allelic frequencies, which are implicated in neurobiological processes. Second, genetic studies strongly suggest that ADHD diagnosis shares a large proportion of genetic risks with continuously distributed traits of ADHD in the population, with shared genetic risks also seen across development and sex. Third, ADHD genetic risks are shared with those implicated in many other neurodevelopmental, psychiatric and somatic phenotypes. As sample sizes and the diversity of genetic studies continue to increase through international collaborative efforts, we anticipate further success with gene discovery, characterization of how the ADHD phenotype relates to other human traits and growing potential to use genomic risk factors for understanding clinical trajectories and for precision medicine approaches.

The (Broad-Sense) Genetic Correlations Among Four Measures of Inattention and Hyperactivity in 12 Year Olds

We estimated the genetic covariance matrix among four inattention (INATT) and four hyperactivity (HYP) measures in the classical twin design. Data on INATT and HYP symptom counts were obtained in mono- and dizygotic twin pairs (N = 1593) with an average age of 12.2 years (sd = .51). We analyzed maternal ratings of INATT and HYP based on the Conners' Parent Rating Scale (CPRS), the Strengths and Weaknesses of ADHD-symptoms and Normal-behavior (SWAN), and teacher ratings based on the Conners' Teacher rating scale (CTRS) and the ASEBA Teacher Rating Form (TRF). Broad-sense heritabilities, corrected for the main effects of sex and for random teacher rater effects, were large (ranging from .658 to .912). The results reveal pervasive and strong broad-sense genetic effects on INATT and HYP phenotypes with the phenotypic covariance among the phenotypes largely due to correlated genetic effects. Specifically between 79.9 and 99.9% of the phenotypic covariance among the HYP measures, and between 81.0 and 93.5% of the INATT measures are attributable to broad-sense genetic effects. Overall, the present results, pertaining to the broad-sense heritabilities and shared genetic effects, support the current genome-wide association meta-analytic approach to identifying pleiotropic genetic variants.

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.

Treatment Approaches to Attention Deficit Hyperactivity Disorder

Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder in children, adolescents, and adults, with a prevalence estimated from 5% to 7% across cultures and approximately 2% to 5% in adults. This lifelong disorder challenges nurses to understand the basis of ADHD, analyze symptoms, differentiate coexisting disorders, gather health information from varied sources, and implement person-centered multimodal treatment. Nurses are poised to plan, and work with patients, families, and teachers in the community and school systems to optimize academic and occupational performance and improve quality of life. Pharmacotherapy, psychoeducation, and behavioral therapies are strong components of multimodal treatment planning.

Persistence and innovation effects in genetic and environmental factors in negative emotionality during infancy: A twin study

Background

Difficult temperament in infancy is a risk factor for forms of later internalizing and externalizing psychopathology, including depression and anxiety. A better understanding of the roots of difficult temperament requires assessment of its early development with a genetically informative design. The goal of this study was to estimate genetic and environmental contributions to individual differences in infant negative emotionality, their persistence over time and their influences on stability between 5 and 18 months of age.

Method

Participants were 244 monozygotic and 394 dizygotic twin pairs (49.7% male) recruited from birth. Mothers rated their twins for negative emotionality at 5 and 18 months. Longitudinal analysis of stability and innovation between the two time points was performed in Mplus.

Results

There were substantial and similar heritability (approximately 31%) and shared environmental (57.3%) contributions to negative emotionality at both 5 and 18 months. The trait’s interindividual stability across time was both genetically- and environmentally- mediated. Evidence of innovative effects (i.e., variance at 18 months independent from variance at 5 months) indicated that negative emotionality is developmentally dynamic and affected by persistent and new genetic and environmental factors at 18 months.

Conclusions

In the first two years of life, ongoing genetic and environmental influences support temperamental negative emotionality but new genetic and environmental factors also indicate dynamic change of those factors across time. A better understanding of the source and timing of factors on temperament in early development, and role of sex, could improve efforts to prevent related psychopathology.

The opposite end of the attention deficit hyperactivity disorder continuum: genetic and environmental aetiologies of extremely low ADHD traits

BACKGROUND

Although attention deficit hyperactivity disorder (ADHD) is thought to reflect a continuously distributed quantitative trait, it is assessed through binary diagnosis or skewed measures biased towards its high, symptomatic extreme. A growing trend is to study the positive tail of normally distributed traits, a promising avenue, for example, to study high intelligence to increase power for gene-hunting for intelligence. However, the emergence of such a 'positive genetics' model has been tempered for ADHD due to poor phenotypic resolution at the low extreme. Overcoming this methodological limitation, we conduct the first study to assess the aetiologies of low extreme ADHD traits.

METHODS

In a population-representative sample of 2,143 twins, the Strength and Weaknesses of ADHD Symptoms and Normal behaviour (SWAN) questionnaire was used to assess ADHD traits on a continuum from low to high. Aetiological influences on extreme ADHD traits were estimated using DeFries-Fulker extremes analysis. ADHD traits were related to behavioural, cognitive and home environmental outcomes using regression.

RESULTS

Low extreme ADHD traits were significantly influenced by shared environmental factors (23-35%) but were not significantly heritable. In contrast, high-extreme ADHD traits showed significant heritability (39-51%) but no shared environmental influences. Compared to individuals with high extreme or with average levels of ADHD traits, individuals with low extreme ADHD traits showed fewer internalizing and externalizing behaviour problems, better cognitive performance and more positive behaviours and positive home environmental outcomes.

CONCLUSIONS

Shared environmental influences on low extreme ADHD traits may reflect passive gene-environment correlation, which arises because parents provide environments as well as passing on genes. Studying the low extreme opens new avenues to study mechanisms underlying previously neglected positive behaviours. This is different from the current deficit-based model of intervention, but congruent with a population-level approach to improving youth wellbeing.

Head Motion and Inattention/Hyperactivity Share Common Genetic Influences: Implications for fMRI Studies of ADHD

Head motion (HM) is a well known confound in analyses of functional MRI (fMRI) data. Neuroimaging researchers therefore typically treat HM as a nuisance covariate in their analyses. Even so, it is possible that HM shares a common genetic influence with the trait of interest. Here we investigate the extent to which this relationship is due to shared genetic factors, using HM extracted from resting-state fMRI and maternal and self report measures of Inattention and Hyperactivity-Impulsivity from the Strengths and Weaknesses of ADHD Symptoms and Normal Behaviour (SWAN) scales. Our sample consisted of healthy young adult twins (N = 627 (63% females) including 95 MZ and 144 DZ twin pairs, mean age 22, who had mother-reported SWAN; N = 725 (58% females) including 101 MZ and 156 DZ pairs, mean age 25, with self reported SWAN). This design enabled us to distinguish genetic from environmental factors in the association between head movement and ADHD scales. HM was moderately correlated with maternal reports of Inattention (r = 0.17, p-value = 7.4E-5) and Hyperactivity-Impulsivity (r = 0.16, p-value = 2.9E-4), and these associations were mainly due to pleiotropic genetic factors with genetic correlations [95% CIs] of rg = 0.24 [0.02, 0.43] and rg = 0.23 [0.07, 0.39]. Correlations between self-reports and HM were not significant, due largely to increased measurement error. These results indicate that treating HM as a nuisance covariate in neuroimaging studies of ADHD will likely reduce power to detect between-group effects, as the implicit assumption of independence between HM and Inattention or Hyperactivity-Impulsivity is not warranted. The implications of this finding are problematic for fMRI studies of ADHD, as failing to apply HM correction is known to increase the likelihood of false positives. We discuss two ways to circumvent this problem: censoring the motion contaminated frames of the RS-fMRI scan or explicitly modeling the relationship between HM and Inattention or Hyperactivity-Impulsivity.

Factor structure and aetiological architecture of the BRIEF: A twin study

Executive function is a broad construct that encompasses various processes involved in goal-directed behaviour in non-routine situations (Banich, 2009). The present study uses a sample of 560 5- to 16-year-old twin pairs (M = 11.14, SD = 2.53): 219 monozygotic twin pairs (114 female; 105 male) and 341 dizygotic twin pairs (136 female, 107 male; 98 opposite sex) to extend prior literature by providing information about the factor structure and the genetic and environmental architecture of the Behavior Rating Inventory of Executive Function (BRIEF; Gioia et al., 2000, Child Neuropsychol., 6, 235; Gioia et al., 2000, Behavior rating inventory of executive function, Lutz, FL: Psychological Assessment Resources), a multifaceted rating scale of everyday executive functions. Phenotypic results revealed a 9-scale, 3-factor model best represents the BRIEF structure within the current sample. Results of the genetically sensitive analyses indicated the presence of rater bias/contrast effects for the Initiate, Working Memory, and Task-Monitor scales. Additive genetic and non-shared environmental influences were present for the Initiate, Plan/Organize, Organization of Materials, Shift, and Monitor and Self-Monitor scales. Influences on Emotional Control were solely environmental. Interestingly, the aetiological architecture observed was similar to that of performance-based measures of executive function. This observed similarity provided additional evidence for the usefulness of the BRIEF as a measure of 'everyday' executive function.

Heritability of attention-deficit hyperactivity disorder in adults

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. Symptoms often persist into adulthood, with a prevalence of 2.5-5% in adult populations. Twin studies in childhood consistently report high heritabilities of 70-80%, while studies in adult samples show only moderate heritability of 30-40% when estimated from self-ratings. This review summarizes the available research on the heritability of ADHD in adults. Three key findings are outlined: (i) self-ratings lead to relatively low heritability estimates of ADHD, independent of age and whether ratings refer to current or retrospective symptoms; (ii) studies relying on different informants to rate each twin within a pair (i.e., self-ratings and different parents/teachers rating each twin in a pair) consistently yield lower heritability estimates than studies relying on ratings from a single informant; (iii) studies using cross-informant data via either combined parent and self-ratings or clinical diagnoses information suggest that the heritability of ADHD in adults could be as high as 70-80%. Together, the reviewed studies suggest that the previously reported low heritability of ADHD in adults is unlikely to reflect a true developmental change. Instead, the drop in heritability is better explained by rater effects related to a switch from using one rater for both twins in a pair (parent/teacher) in childhood, to relying on self-ratings (where each twin rates themselves) of ADHD symptoms in adulthood. When rater effects are addressed using cross-informant approaches, the heritability of ADHD in adults appears to be comparable to the heritability of ADHD in childhood. © 2015 Wiley Periodicals, Inc.