Subjects were recruited from Yale University School of Medicine (APT Foundation, New Haven, Connecticut), the University of Connecticut Health Center (Farmington), McLean Hospital (Harvard Medical School, Belmont, Massachusetts), and the Medical University of South Carolina (Charleston) into 1 of 2 study arms. Six hundred thirty-two families ascertained through affected sibling pairs that met DSM-IV criteria for CD or opioid dependence as previously described,15,21,25 containing at least 1 examined sibling with CD or CIP, formed the discovery sample. Of the 632 families, 119 had at least 1 sibling pair discordant for CD and 319 had at least 1 sibling pair discordant for CIP. Of the 1612 genotyped subjects, 160 were parents (9.9%) (and the remainder were siblings) and 141 did not contribute information about substance dependence (8.7%). An independent group of 2073 unrelated subjects recruited for studies of CD (n=667), opioid dependence (n=103), or alcohol dependence (n=1303) were included in a replication sample. Genetic studies of CD and related traits in a subset of this sample have been published.10,23
