Comorbid psychopathology in parents and twins was also examined. Histories of DSM-IV conduct disorder (CD) and major depressive disorder (MDD) in either parent were coded from parent self-report, with two dummy variables to distinguish affected parents from those with missing paternal and maternal self-report data. Parental smoking was coded from parent self- and coparent reports as well as twin report at Waves 1, 3, and 4. Among offspring psychopathologies, we examined history of DSM-IV inattention, hyperactivity, oppositional defiant disorder (ODD), CD, social anxiety disorder (SAD), MDD and a non-diagnostic measure of suicidality (ideation, plan or attempt). CD, SAD, MDD and suicidality, including ages of onset, were assessed by twin self-report at Waves 1, 3 and 4. Inattention, hyperactivity and ODD were queried in the parent interview, with two dummy variables to distinguish affected twins from those with missing parent-report data.
