Validity and reliability of the Severity of Dependence Scale (SDS) in a Brazilian sample of drug users.

The Severity of Dependence Scale (SDS) is a short, five-item scale which provides a measure of degree of dependence upon different drugs. The present study explores the validity and reliability of a Portuguese version of the instrument with a sample of 374 Brazilian drug users. Concurrent validity of the SDS was assessed in relation to reported quantity of drugs used and to DSM-IV dependence items, and test-retest reliability was assessed with a subsample of 42 subjects. The SDS total scores for powder cocaine, crack cocaine, cannabis and alcohol were significantly and highly positively correlated with severity of dependence as measured by DSM-IV, and with the estimated quantity of drugs used in the last month. Test-retest coefficients were high for all drugs studied. Principal components analysis showed that the SDS scores lie on a single dimension with the exception of crack cocaine where scores lie on a single dimension for treatment attenders and on two dimensions for community samples. The results indicate that the Portuguese version of the SDS is a valid research tool for measuring severity of dependence upon powder cocaine (snorted), crack cocaine (smoked), cannabis and alcohol.