Background. An obstacle to the successful
classification of attention deficit hyperactivity disorder (ADHD) is
the frequently reported co-morbidity between ADHD and conduct disorder
(CD). Prior work suggested that from a familial perspective, ADHD
children with CD may be aetiologically distinct from those without
CD.Methods. Using family study methodology and three
longitudinal assessments over 4 years, we tested hypotheses about
patterns of familial association between ADHD, CD, oppositional
defiant disorder (ODD) and adult antisocial personality disorder
(ASPD).Results. At the 4-year follow-up, there were 34 children
with lifetime diagnoses of ADHD + CD, 59 with ADHD + ODD and 33 with
ADHD only. These were compared with 92 non-ADHD, non-CD, non-ODD
control probands. Familial risk analysis revealed the following: (1)
relatives of each ADHD proband subgroup were at significantly greater
risk for ADHD and ODD than relatives of normal controls; (2) rates
of CD and ASPD were elevated among relatives of ADHD + CD probands
only; (3) the co-aggregation of ADHD and the antisocial disorders could
not be accounted for by marriages between ADHD and antisocial spouses;
and (4) both ADHD and antisocial disorders occurred in the same
relatives more often than expected by chance alone.Conclusions. These findings suggest that ADHD with and
without antisocial disorders may be aetiologically distinct disorders
and provide evidence for the nosologic validity of ICD-10 hyperkinetic
conduct disorder.
