Substance misuse and comorbid psychopathology in a high-risk group: a study of siblings of cocaine misusers.

Vulnerability to drug misuse and psychopathology was explored among 673 siblings of 298 opioid-addicted probands. Disorders were evaluated based on family history information obtained from the proband. Results indicated that (1) siblings of cocaine misusers showed high vulnerability to developing drug misuse, alcoholism, and antisocial personality disorder; (2) siblings of probands with specific comorbid diagnoses were vulnerable to developing a range of disorders (no specificity of aggregation was found); (3) proband major depression was related to a broad spectrum of sibling disorders; (4) the presence of a major psychiatric disorder was strongly associated with substance misuse among siblings; (5) psychopathology appeared to precede drug misuse in terms of age of onset. These findings corroborate those previously obtained with siblings of opioid addicts, and they are discussed in terms of implications for the classification and treatment of substance misuse.