A systematic evaluation of ADHD and comorbid psychopathology in a population-based twin sample.
OBJECTIVE
Clinical and population samples demonstrate that attention-deficit/hyperactivity disorder (ADHD) occurs with other disorders. Comorbid disorder clustering within ADHD subtypes is not well studied.


METHODS
Latent class analysis (LCA) examined the co-occurrence of DSM-IV ADHD, oppositional defiant disorder (ODD), conduct disorder (CD), and depression symptoms in a population twin sample. The authors fit separate models for ADHD and comorbid disorder symptoms. Twin concordance ratios (monozygotic versus dizygotic) were compared examining genetic influence on class membership.


RESULTS
LCA of ADHD symptoms resulted in seven classes including inattentive, combined, and hyperactive subtypes in 1,616 subjects. The few ADHD symptoms (53.4%) and severe inattentive (12.3%) classes were most frequent. LCA of ODD, CD, and depression symptoms in 1,587 subjects revealed five classes including ODD (19.4%), depression (14.5%), and two composite classes: ODD/CD (6.9%) and ODD/CD/depression (7.2%). Internalizing and externalizing comorbid disorders were present across all ADHD subtypes. Odds ratios (ORs) for twin concordance indicate genetic influence on severe inattentive (OR = 4.18; 95% confidence interval [CI], 1.52-11.53) and combined (OR = 5.25; 95% CI, 1.32-20.78) ADHD classes and ODD (OR = 1.49; 95% CI, 0.70-3.17), ODD/CD (OR = 3.32; 95% CI, 0.57-19.28), and ODD/CD/depression (OR = 1.20; 95% CI, 0.30-4.77) classes.


CONCLUSIONS
Internalizing and externalizing disorders did not cluster differentially within ADHD subtypes. LCA may provide a more precise characterization of comorbidity with ADHD.
Volk
Heather E
HE
Doctoral Program in Public Health Studies, Saint Louis University School of Public Health, St. Louis, MO 63110, USA.
Neuman
Rosalind J
RJ
Todd
Richard D
RD
D000293:Adolescent; D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000453:epidemiology* / Q000235:genetics; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000145:classification / Q000453:epidemiology* / Q000235:genetics; D002648:Child; D015897:Comorbidity; D019955:Conduct Disorder / Q000145:classification / Q000453:epidemiology* / Q000235:genetics; D003866:Depressive Disorder / Q000145:classification / Q000453:epidemiology* / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008923:Missouri / Q000453:epidemiology; D016017:Odds Ratio; D010641:Phenotype; D015995:Prevalence; D014429:Twins, Dizygotic / Q000523:psychology*; D014430:Twins, Monozygotic / Q000523:psychology*