Yale-Penn participants were recruited for studies of the genetics of drug or alcohol dependence in five eastern U.S. centers as described elsewhere14–16. Subjects gave written informed consent as approved by the institutional review board at each site. Subjects were evaluated with the semi-structured assessment for drug dependence and alcoholism (SSADDA) to derive diagnostic and statistical manual of mental disorders, fourth edition (DSM-IV) lifetime SD diagnoses, and other major psychiatric traits. In the present study, we used information regarding DSM-IV SD diagnoses and criterion counts related to alcohol dependence (AD), cannabis dependence (CaD), cocaine dependence (CoD), nicotine dependence (ND), and opioid dependence (OD). Detailed information regarding these phenotypic definitions is provided in our previous studies14–16. Data regarding suicidality outcomes were derived from SSADDA items: SI “Have you ever thought about killing yourself? [Yes/No]”; persistent SI “Did those thoughts persist for at least 7 days in a row? [Yes/No]”; SP “Did you have a plan? [Yes/No]”; and SA “Have you ever tried to kill yourself? [Yes/No]”. Individuals not reporting SI were not asked about persistent SI and SP. Accordingly, individuals who did
