Abstract
Familial risk for psychiatric disorders was assessed among 673 siblings of cocaine-abusing individuals. Various indices of familial risk were examined, including those based on the presence/absence of disorders in parents and those reflecting severity (assessed by age at onset) of disorders. Across risk indices, the findings indicated high vulnerability among siblings (1) to substance abuse in relation to paternal alcoholism and (2) to depression and substance abuse in relation to maternal depression. The validity of the Type I/Type II distinction was upheld in the context of alcoholism only among fathers. In the context of affective disorders, risk to offspring was greatest if exposure to parental psychopathology occurred during the early childhood years.