Age-of-onset classification of conduct disorder: Reliability and validity in a prospective cohort study

Objective: To test in a prospective clinical cohort study the reliability a nd validity of the age-of-onset subtyping of conduct disorder. Method: Part icipants were adolescents referred to psychiatric clinics who met DSM-III-R criteria for conduct disorder by structured diagnostic interview. Age of o nset was the reported age of the first conduct disorder symptom. The reliab ility of age-of-onset report was tested by assessing agreement within infor mant on interviews 2 to 4 weeks apart. Age-of-onset groups were compared wi thin informant on rates of correlates and symptom and social functioning ou tcomes over a period of 3 years. Results: The reliability of age-of-onset r eport was low (kappa of 0.1 and 0.4 by adolescent and parent informant, res pectively). Although the early-onset group had elevated rates of attention- deficit/hyperactivity disorder, family disadvantage, and aggressive and non aggressive antisocial behaviors at inclusion, growth curve analysis showed that age-of-onset subtyping had no predictive validity Conclusions: The rel iability of ascertainment of age of onset of antisocial behavior requires f urther study. While age-of-onset subtyping has heuristic value with respect to the study of the causal pathways to conduct disorder, it is premature t o use this system in clinic settings.