Genetic and Environmental Influences on the Associations Between Attention Problems and Other Problem Behaviors

Does Co-Occurring Anxiety Modulate ADHD-Related Cognitive and Neurophysiological Impairments?

Objective: This study investigates whether anxiety modulates cognitive-performance, electrophysiological and electrodermal processes that we previously found impaired in individuals with ADHD. Method: Self-reported anxiety symptoms, cognitive-electrophysiological measures of response inhibition, working memory, attention, conflict monitoring, error processing, and peripheral arousal during three cognitive tasks were obtained from 87 adolescents and young adults with ADHD and 169 controls. We tested the association of anxiety symptoms with each measure and whether controlling for anxiety symptoms attenuates the ADHD-control difference for each measure. Results: Individuals with ADHD showed significantly elevated anxiety symptoms compared with controls. Only commission errors on a Continuous Performance Test (measuring response inhibition) were significantly associated with anxiety symptoms and only among controls, with the ADHD-control difference in this measure remaining significant. Conclusion: Using a wide range of cognitive, electrophysiological, and electrodermal measures, our investigation suggests, overall, limited malleability of these impairments in individuals with ADHD irrespective of their levels of anxiety.

Investigating regions of shared genetic variation in attention deficit/hyperactivity disorder and major depressive disorder: a GWAS meta-analysis

Attention deficit/hyperactivity disorder (ADHD) demonstrates a high level of comorbidity with major depressive disorder (MDD). One possible contributor to this is that the two disorders show high genetic correlation. However, the specific regions of the genome that may be responsible for this overlap are unclear. To identify variants associated with both ADHD and MDD, we performed a meta-analysis of GWAS of ADHD and MDD. All genome wide significant (p < 5 × 10^–8) SNPs in the meta-analysis that were also strongly associated (p < 5 × 10^–4) independently with each disorder were followed up. These putatively pleiotropic SNPs were tested for additional associations across a broad range of phenotypes. Fourteen linkage disequilibrium-independent SNPs were associated with each disorder separately (p < 5 × 10^–4) and in the cross-disorder meta-analysis (p < 5 × 10^–8). Nine of these SNPs had not been highlighted previously in either individual GWAS. Evidence supported nine of the fourteen SNPs acting as eQTL and two as brain eQTL. Index SNPs and their genomic regions demonstrated associations with other mental health phenotypes. Through conducting meta-analysis on ADHD and MDD only, our results build upon the previously observed genetic correlation between ADHD and MDD and reveal novel genomic regions that may be implicated in this overlap.

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.

Aetiological overlap between anxiety and attention deficit hyperactivity symptom dimensions in adolescence

BACKGROUND

Anxiety and attention-deficit/hyperactivity (ADH) problems are common in adolescence, often co-occur, and are characterised by high heterogeneity in their phenotypic expressions. Although it is known that anxiety and ADH problems correlate, the relationships between subtypes of anxiety and ADH problems have been scarcely investigated.

METHODS

Using a large population sample of adolescent twins and siblings we explored the phenotypic and aetiological association between anxiety subtypes (panic/agoraphobia, separation anxiety, social anxiety, physical injury fears, obsessive-compulsive symptoms and generalised anxiety) and the two ADH dimensions (attention problems and hyperactivity/impulsivity). Both phenotypes were assessed using self-report questionnaires.

RESULTS

The association between ADH problems and anxiety could be entirely attributed to attention problems, not hyperactivity/impulsivity. Most of the correlations between anxiety subtypes and attention problems showed an approximately equal role of genetic and nonshared environmental factors.

CONCLUSIONS

The high heterogeneity within anxiety and ADH problems should be taken into account in order to better understand comorbidity between them.

Genetic Influences on Thought Problems in 7-Year-Olds: A Twin-Study of Genetic, Environmental and Rater Effects

The Thought–Problem scale (TP) of the CBCL assesses symptoms such as hallucinations and strange thoughts/behaviors and has been associated with other behavioral disorders. This study uses parental reports to examine the etiology of variation in TP, about which relatively little is known, in 7-year-old twins. Parental ratings on TP were collected in 8,962 7-year-old twin pairs. Because the distribution of TP scores was highly skewed scores were categorized into 3 classes. The data were analyzed under a threshold liability model with genetic structural equation modeling. Ratings from both parents were simultaneously analyzed to determine the rater agreement phenotype (or common phenotype [TPc]) and the rater specific phenotype [TPs] that represents rater disagreement caused by rater bias, measurement error and/or a unique view of the parents on the child's behavior. Scores on the TP-scale varied as a function of rater (fathers rated fewer problems), sex (boys scored higher) and zygosity (DZ twins scored higher). The TPc explained 67% of the total variance in the parental ratings. Variation in TPc was influenced mainly by the children's genotype (76%). Variance in TPs also showed a contribution of genetic factors (maternal reports: 61%, paternal reports: 65%), indicating that TPs does not only represent rater bias. Shared environmental influences were only found in the TPs. No sex differences in genetic architecture were observed. These results indicate an important contribution of genetic factors to thought problems in children as young as 7 years.

Genetic and Environmental Influences on Stuttering and Tics in Japanese Twin Children

The purpose of this study was to clarify the genetic contribution to stuttering and tics in childhood using the largest databases of Japanese twins. The subjects were 1896 pairs of twin children consisting of 1849 males and 1943 females with a mean age of 11.6 years (3 years to 15 years). All data were gathered by questionnaire. The prevalence of stuttering was 6.7% in males and 3.6% in females (p < .0001). The prevalence of tics was 6.8% in males and 4.1% in females (p = .0021). Concordance rates and polychoric correlations were all higher in monozygotic pairs than in dizygotic pairs irrespective of sex combination. Structural equation modeling showed that the proportion of total phenotypic variance attributable to genetic influences was 80% in males and 85% in females for stuttering, and 28% in males and 29% in females for tics. Moreover, co-occurrence between stuttering and tics was observed in 0.8% of males (tetrachoric correlation: r = .18) and 0.5% of females (r = .31), which was attributed partly (nearly 10% of total genetic variance of each trait) to the common genetic factors, with genetic correlation of r = .32.

Sibling-based association analyses of the serotonin transporter polymorphism and internalizing behavior problems in children

BACKGROUND

Childhood internalizing problems are often precursors in the development of more serious psychiatric syndromes including anxiety and depressive disorders. Twin studies of the etiology of these disorders suggest that the genetic risk factors underlying anxiety and depression are highly correlated. However, the specific genetic mechanisms responsible for this risk have not yet been identified.

METHODS

We examined the association between childhood internalizing problems and a functional polymorphism in the serotonin transporter gene (5-HTTLPR) in 711 children participating in a longitudinal twin study of behavioral and emotional development. Internalizing problems were measured at ages 4, 7, 9, 10, 11 and 12 years using the Child Behavior Checklist (CBCL) parent report form. We applied a sibling-based methodology for estimating allelic association with quantitative traits, while controlling for population stratification.

RESULTS

No associations were found for CBCL Internalizing problems at any age, including the subscales for Somatic Complaints, Withdrawn and Anxiety/Depression.

CONCLUSIONS

Thus, although our results did not support the hypothesis that the 5-HTTLPR contributes to a dimensional expression of internalizing behavior problems, this does not rule out the possibility that it is an interesting polymorphism to pursue in the search for genetic risk factors related to major depressive and/or anxiety disorders.