Family history and diagnosis of alcohol dependence in cocaine dependence

Genetic research in alcoholism has made major advances in recent decades. Twin, adoption, high-risk, and familial studies have demonstrated an inheritance factor in alcoholism. No studies have demonstrated a genetic or familial disposition to cocaine and marijuana dependence. Two hundred sixty-three inpatients were given a structured psychiatric interview retrospectively (150) and prospectively (113) to obtain a DSM-III-R diagnosis of substance dependence disorders in the probands and of alcohol dependence in family members. Our study reveals a large number of probands with cocaine dependence with a positive family history for alcohol dependence. Approximately 50% of probands with cocaine dependence had at least a first or second degree relative with a diagnosis of alcohol dependence when studied by the family history and study methods. As many as 89% of probands who met DSM-III-R criteria for cocaine dependence qualified for other substance dependence diagnoses. Our study finds a high prevalence of alcohol (68% and 89%) and cannabis dependence (53% and 46%) in patients with cocaine dependence. Furthermore, the age of onset of alcohol and other drug dependence is early for those with cocaine dependence and precedes the onset of cocaine dependence. The diagnoses of other alcohol and drug dependence in cocaine dependence and in family members of probands with cocaine dependence have important implications for etiology, prognosis, and treatment.