Psychiatric and alcohol disorders as risk factors for drug abuse. A case-control study among adults in Rio de Janeiro, Brazil.

This study tested the hypothesis that a history of psychiatric and alcohol disorders would affect the risk of developing drug abuse or dependence later in life. This case-control study selected cases and controls using the "snowball" technique in order to obtain cases from this "hidden" population and to match sex, age and friendship. Information was gathered using the Composite International Diagnostic Interview (CIDI), and computer diagnoses were generated according to the DSM-III-R criteria. The study included 370 subjects. Results of the conditional logistic regression analysis showed that having a history of alcohol dependence was independently associated with an increased risk of drug abuse/dependence (OR = 2.6, 95% CI 1.1-6.0) and that this risk was even higher for those whose alcohol dependence occurred in combination with another psychiatric disorder (OR = 4.6, 95% CI 2.1-10.0). An increased risk of drug abuse/dependence was also found for those who were aged 12 years or under when their first psychiatric disorder was manifested (OR = 2.2, 95% CI 1.3-3.7) and among those with two or more psychiatric disorders (OR = 2.5, 95% CI 1.5-4.1). These findings suggest that programmes directed towards the treatment and prevention of drug abuse must be prepared to address psychiatric and alcohol disorders in childhood and adolescence.