mostly mixed-ethnicity families, clustered near the middle. The threshold we used in those cases was 0.5. Individuals with a clinical diagnosis of a major psychotic illness (schizophrenia or schizoaffective disorder) were excluded as probands. When an affected sibling pair was recruited, we also recruited additional siblings and parents, whenever possible, regardless of affection status. Out of a total of 339 AA families, 238 families had at least one subject affected with AD. The sample included 840 genotyped subjects (and a total of 1642 for linkage analysis, including, e.g., ungenotyped parents). 50.4% were male, and age range was 18–79, with a mean of 40.8±7.3 (SD). Family size ranged from 3–13 subjects, with a mean of 4.84. Subjects gave informed consent as approved by the institutional review board at each clinical site, and a certificate of confidentiality for the work was obtained from NIH (NIDA). Family characteristics are shown in Tables 1.
