A case control series of unrelated individuals was selected from over 8,000 subjects who participated in the genetic arm of COGA. COGA systematically recruited subjects from participating centers in Hartford, Connecticut; Indianapolis, Indiana; Iowa City, Iowa; New York City, New York; San Diego, California; St. Louis, Missouri, and Washington DC. For SAGE, cases met life-time criteria for DSM-IV alcohol dependence; the majority of cases were recruited from alcoholism treatment centers. Control subjects, biologically unrelated to cases, were individuals who consumed alcohol, but never experienced any significant alcohol or drug related problems, as reported on the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA). The COGA study contributed 649 nicotine dependent cases and 553 non-nicotine dependent smoking control subjects to the subsequent nicotine dependence genetic analyses.
