Phenotype data for four substances (alcohol, cannabis, cocaine, and opioids) were obtained from the SSAGA. Some individuals were assessed more than once, in which case data from the SSAGA interview at which an individual reported the maximum number of DSM-IV criteria endorsements for the particular substance was used. Two phenotypes were used in the genetic analyses: ANYDEP, a binary aggregate substance dependence phenotype, and QUANTDEP, a quantitative (continuous) substance dependence phenotype developed using factor analysis.
