Dual dependence: assessment of dependence upon alcohol and illicit drugs, and the relationship of alcohol dependence among drug misusers to patterns of drinking, illicit drug use and health problems

AIMS: The study investigates severity of alcohol dependence among drug misusers. Specifically, it investigates the inter-relationship of alcohol and drug dependence and associations with alcohol consumption, drug consumption and substance-related problems. DESIGN, SETTING, PARTICIPANTS: The sample comprised 735 people seeking treatment for drug misuse problems, who were current (last 90 days) drinkers. MEASUREMENTS: Data were collected by structured face-to-face interviews. Dependence upon illicit drugs and upon alcohol was measured by the Severity of Dependence Scale (SDS). FINDINGS: Three groups of drinkers were identified: non-alcohol-dependent drug misusers (63%); low-dependence (19%); and high-dependence (18%). Many drug misusers were drinking excessively and alcohol dependence was related to patterns of alcohol and drug consumption. High-dependence drinkers were more likely to drink extra-strength beer; they were less frequent users of heroin and crack cocaine but more frequent users of benzodiazepines, amphetamines and cocaine powder; they reported more psychological and physical health problems. The SDS was found to have good reliability and validity as a measure of alcohol dependence. SDS scores for alcohol and drug dependence were unrelated. CONCLUSIONS: Alcohol use is an important and under-rated problem in the treatment of drug misusers. A comprehensive assessment of alcohol use among drug misusers should include separate assessments of alcohol consumption, alcohol-related problems and severity of alcohol dependence.