Childhood conduct disorder (CD), lifetime history of major depressive disorder (MDD), and suicide attempt and panic attack histories were included among psychiatric control variables, each assessed as part of the SSAGA. For both cohorts, relaxed criteria were used to diagnose CD, defined as three or more DSM-IV CD symptoms each with onset before age 18. Likewise, the broader construct of panic attack, rather than panic disorder, was used. For Cohort I, as with AD, DSM-IV criteria were applied to DSM-III-R assessment of MDD and panic attack. For Cohort II, DSM-IV MDD and panic attack were directly assessed. Age of onset of MDD was defined as age at first clustering of five or more DSM-IV major depressive symptoms in an episode of at least two weeks duration. For panic attack, age of onset was defined as age at first discrete period of unexpected intense fear or discomfort, in which respondents experienced three or more DSM-IV panic attack symptoms. Equivalent measures of age of onset of MDD and panic attack were not available for Cohort I. For both cohorts, history of suicide attempt was assessed, but only in Cohort II was age of onset available.
