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OBJECTIVE: This longitudinal study of a nonreferred, population-based sample tested the concurrent, convergent, and predictive validity of DSM-IV conduct disorder in children 4(1/2)-5 years of age. METHOD: In the Environmental Risk Longitudinal Twin Study, a representative birth cohort of 2,232 children, the children's mothers were interviewed and the teachers completed mailed questionnaires to assess the children's past 6-month conduct disorder symptoms. Children with three or more symptoms were diagnosed with conduct disorder, and a subset with five or more symptoms was diagnosed with "moderate-to-severe" conduct disorder. RESULTS: The prevalence of conduct disorder and moderate-to-severe conduct disorder were 6.6% and 2.5%, respectively. Children diagnosed with conduct disorder were significantly more likely than comparison subjects to self-report antisocial behaviors, to behave disruptively during observational assessment, and to have risk factors known to be associated with conduct disorder in older children (effect sizes ranging from 0.26 to 1.24). Five-year-olds diagnosed with conduct disorder were significantly more likely than comparison subjects to have behavioral and educational difficulties at age 7. Increased risk for educational difficulties at age 7 persisted after control for IQ and attention deficit hyperactivity disorder diagnosis at age 5. CONCLUSIONS: Behavioral problems of preschool-age children meeting diagnostic criteria for conduct disorder should not be ignored. Appropriate intervention should be provided to prevent ongoing behavioral and academic problems.
Kim‐Cohen et al. (2005) studied this question.