Relative Influence of Genetics and Shared Environment on Child Mental Health Symptoms Depends on Comorbidity

<div><p>Background</p><p>Comorbidity among childhood mental health symptoms is common in clinical and community samples and should be accounted for when investigating etiology. We therefore aimed to uncover latent classes of mental health symptoms in middle childhood in a community sample, and to determine the latent genetic and environmental influences on those classes.</p><p>Methods</p><p>The sample comprised representative cohorts of twins. A questionnaire-based assessment of mental health symptoms was used in latent class analyses. Data on 3223 twins (1578 boys and 1645 girls) with a mean age of 7.5 years were analyzed. The sample was predominantly non-Hispanic Caucasian (92.1%).</p><p>Results</p><p>Latent class models delineated groups of children according to symptom profiles–not necessarily clinical groups but groups representing the general population, most with scores in the normative range. The best-fitting models suggested 9 classes for both girls and boys. Eight of the classes were very similar across sexes; these classes ranged from a “Low Symptom” class to a “Moderately Internalizing & Severely Externalizing” class. In addition, a “Moderately Anxious” class was identified for girls but not boys, and a “Severely Impulsive & Inattentive” class was identified for boys but not girls. Sex-combined analyses implicated moderate genetic influences for all classes. Shared environmental influences were moderate for the “Low Symptom” and “Moderately Internalizing & Severely Externalizing” classes, and small to zero for other classes.</p><p>Conclusions</p><p>We conclude that symptom classes are largely similar across sexes in middle childhood. Heritability was moderate for all classes, but shared environment played a greater role for classes in which no one type of symptom predominated.</p></div

Proportion of variance accounted for (confidence intervals) and model fit of biometric twin models for girls and boys combined.

a<p>A, C, and E refer to proportion of variance accounted for by additive genetic, shared environment and unique environment, respectively.</p><p>Abbreviations: Sat = saturated model; ACE = twin model; LL = log-likelihood; Δχ<b><i>²</i></b> = delta chi square;</p><p>*p<.05,</p><p>**p<.01,</p><p>***p<.001.</p

Item response plots for girls’ latent classes G5 and G1–G4 (upper panel) and girls’ latent classes G5 and G6–G9 (lower panel).

<p>Abbreviations: DE = Depression; OA = Overanxiousness; SA = Separation Anxiety; CN = Conduct Problems; OD = Oppositional Defiant Problems; IM = Impulsivity; AT = Inattention.</p

Item response plots for boys’ latent classes B1 and B2–B5 (upper panel) and boys’ latent classes B1 and B6–B9 (lower panel).

<p>Abbreviations: DE = Depression; OA = Overanxiousness; SA = Separation Anxiety; CN = Conduct Problems; OD = Oppositional Defiant Problems; IM = Impulsivity; AT = Inattention.</p

Weighted^a averages of external covariates for girls, by latent class.

a<p>Weighted by class membership probabilities.</p>b<p>Income categories: 8 = $40,001 to$45,000; 9 = $45,001 to$50,000; 10 = $50,001 to$60,000; 11 = $60,001 to$70,000; 12 = $70,001 to$80,000.</p>c<p>Self Impairment Scale ranges from 0 (no impairment) to 1.9 (highest observed impairment) and Family Impairment Scale ranges from 0 (no impairment) to 2.8 (highest observed impairment).</p>d<p>Any diagnosis refers to a diagnosis of MDD, GAD, SAD, CD, ODD, or ADHD.</p><p>Abbreviations: MDD = Major Depressive Disorder; GAD = Generalized Anxiety Disorder; SAD = Separation Anxiety Disorder; CD = Conduct Disorder; ODD = Oppositional Defiant Disorder; ADHD = Attention-Deficit/Hyperactivity Disorder.</p

Weighted^a averages of external covariates for boys, by latent class.

a<p>Weighted by class membership probabilities.</p>b<p>Income categories: 8 = $40,001 to$45,000; 9 = $45,001 to$50,000; 10 = $50,001 to$60,000; 11 = $60,001 to$70,000; 12 = $70,001 to$80,000.</p>c<p>Self Impairment scale ranges from 0 (no impairment) to 1.9 (highest observed impairment) and Family Impairment Scale ranges from 0 (no impairment) to 3.0 (highest observed impairment).</p>d<p>Any diagnosis refers to a diagnosis of MDD, GAD, SAD, CD, ODD, or ADHD.</p><p>Abbreviations: MDD = Major Depressive Disorder; GAD = Generalized Anxiety Disorder; SAD = Separation Anxiety Disorder;</p><p>CD = Conduct Disorder; ODD = Oppositional Defiant Disorder; ADHD = Attention-Deficit/Hyperactivity Disorder.</p