Our control samples (662 white subjects [46% male and 54% female]) originated from 3 independent sources: (1) undergraduate students (270 self-declared healthy white students) from a large Southeastern university who participated in a separate study of genes and personality in return for partial course credit; (2) Coriell Cell Repository, Camden, New Jersey (200 self-declared healthy white Americans); and (3) European Collection of Cell Cultures (Sigma-Aldrich, St Louis, Missouri; 192 apparently healthy white blood donors in the United Kingdom). The male to female ratio did not significantly differ between cases and controls (χ12=0.72; P>.05). We cannot rule out the occurrence of OCD within the second and third control groups, as self-report and standard scales were used for evaluation of only the first group. Genotypic and allelic frequencies did not significantly differ between these 3 control groups (data not shown). All studies were conducted under protocols approved by the institutional review board at the National Institute of Mental Health Division of Intramural Research Programs and by the Human Subjects Committee at Florida State University. Additional details on proband and control samples have been described previously.29,30
