Community-based participants were matched on all four criteria (i.e., year of birth, gender, ethnicity, and zip code) for 96.5% of cocaine dependent cases. The current analyses included only matched cocaine dependent cases and community-based participants. The total sample comprised 918 participants: 459 cocaine dependent cases and 459 community-based comparison participants. Sibling data were not included in these analyses because the focus of these analyses was on the case-community cohort design rather than familial transmission.
