BACKGROUND: Conduct disorder is considered difficult to treat, but comorbid psychiatric disorders may be a basis for treating some youths with conduct disorder. We sought to identify patterns of comorbid psychiatric diagnoses and psychopathology associated with conduct disorder by reported age-of-onset.

METHODS: Referred children and adolescents, aged 4-17 years old, were clinically evaluated. Ages of onset of CD symptoms (N=53) were ascertained and divided according to DSM-IV criteria as childhood onset (old) or adolescent onset (>or=10 years old).

RESULTS: Childhood-onset conduct disorder was associated with higher rates of ADHD and anxiety disorders, male gender, and perceived and total hostility scores than adolescent-onset conduct disorder. Adolescent-onset was associated with higher rates of PTSD, alcohol and substance use disorders, complex comorbidity (i.e., 6+ diagnoses lifetime), and female gender.

CONCLUSIONS: Understanding age-of-onset-related patterns of comorbidity may facilitate psychiatric treatment planning in children and adolescents with conduct disorder.