A replicated molecular genetic basis for subtyping antisocial behavior in children with attention-deficit/hyperactivity disorder.
CONTEXT
Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous neurodevelopmental disorder that in some cases is accompanied by antisocial behavior.


OBJECTIVE
To test if variations in the catechol O-methyltransferase gene (COMT) would prove useful in identifying the subset of children with ADHD who exhibit antisocial behavior.


DESIGN
Three independent samples composed of 1 clinical sample of ADHD cases and 2 birth cohort studies.


PARTICIPANTS
Participants in the clinical sample were drawn from child psychiatry and child health clinics in England and Wales. The 2 birth cohort studies included 1 sample of 2232 British children born in 1994-1995 and a second sample of 1037 New Zealander children born in 1972-1973.


MAIN OUTCOME MEASURES
Diagnosis of ADHD and measures of antisocial behavior.


RESULTS
We present replicated evidence that the COMT valine/methionine polymorphism at codon 158 (COMT Val158Met) was associated with phenotypic variation among children with ADHD. Across the 3 samples, valine/valine homozygotes had more symptoms of conduct disorder, were more aggressive, and were more likely to be convicted of criminal offenses compared with methionine carriers.


CONCLUSIONS
The findings confirm the presence of genetic heterogeneity in ADHD and illustrate how genetic information may provide biological evidence pointing to clinical subtypes.