Attention-deficit hyperactivity disorder subtypes and comorbid disruptive behaviour disorders in a child and adolescent mental health clinic.

OBJECTIVE: To assess demographic characteristics and patterns of comorbid disruptive behavior disorders (oppositional defiant disorder [ODD] or conduct disorder [CD]) in subtypes of attention-deficit hyperactivity disorder (ADHD).
METHOD: One hundred youths consecutively referred to a community child and adolescent mental health clinic and subsequently diagnosed with ADHD by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria were evaluated. The diagnosis was made by a child psychiatrist and was based on information from physicians, parents, teachers, and diagnostic interviews with the youth and their parents.
RESULTS: The major findings were: 1) ADHD combined (C) type was diagnosed in 78% of the subjects, while 15% had inattentive (1) type and 7% had hyperactive-impulsive (HI) type; and 2) patterns of comorbid disruptive behavioural disorders significantly differed among subtypes. Specifically, subjects with the I type showed lower rates of comorbid ODD than those with the C type (33% and 85%; P < 0.001) and HI type (33% and 100%; P = 0.005); subjects with the HI type displayed a higher prevalence of CD than those with the I type (57% and 0%; P = 0.005) and C type (57% and 8%; P = 0.003). These results should be considered tentative because the reliability of the diagnostic procedures was not formally assessed and the number of subjects in the I and HI groups was small.
CONCLUSION: ADHD subtypes showed significant differences in the distribution of comorbid disruptive behaviour disorders. These results support the utility of ADHD subtypes but should be replicated with a larger sample of I and HI type subjects using more rigorous diagnostic methods.