parent report and child self-report of the major DSM-IV diagnostic categories pertinent to youths. Adolescents and parents were interviewed in person or by telephone about half the time. All interviews with children 12 years and younger were in person. DSM-IV diagnoses of ADHD were based upon parental reports (most of the time, maternal). Families were excluded if a parent/guardian reported mental retardation or if the parent/guardian and twins could not speak English. 7
