At each assessment up to 16 the child and primary caretaker (usually the mother) were separately interviewed using the Child and Adolescent Psychiatric Assessment (CAPA) (Angold & Costello, 2000). The Young Adult Psychiatric Assessment (YAPA) (Angold et al., 2009) was used to interview participants at ages 19 and 21. These instruments assess psychiatric symptoms and diagnoses over the preceding 3 months using DSM-IV criteria. Age of onset was collected at each assessment with reference to each symptom endorsed. A binary variable indexing the presence of ODD using full DSM-IV diagnostic criteria, including symptom count threshold, 6-month duration and the presence of psychosocial impairment was employed here. All DSM-IV CD symptoms were measured with the exception that staying out late was not assessed at the first wave as this was conducted before DSM-IV was finalized. DSM-IV symptoms were assessed over the standard CAPA 3 month period rather than 12 months to ensure consistency across the interview. We used a binary variable indexing DSM-IV CD including requirements for both symptom severity and duration.
