Cocaine dependent cases were systematically recruited from chemical dependency treatment units in the greater St. Louis metropolitan area. Community based control subjects were identified through the Missouri Family Registry and matched by age, race, gender, and residential zip code. Controls were biologically unrelated individuals from the same communities who consumed alcohol, but had no lifetime history of dependence on any substance. FSCD contributed 370 nicotine dependent cases and 436 non-nicotine dependent smoking control subjects.
