Abstract
Intravenous drug use is a major vector of HIV transmission. We assessed whether contingency management (CM), in which participants earn reinforcers for drug abstinence, reduces HIV risk behaviors in methadone-maintained opiate- and cocaine-using outpatients. Participants (n=116) were randomly assigned to prize-based CM or to receipt of prize draws noncontingently on a schedule yoked to the CM group. Both groups received methadone and individual counseling throughout treatment. The HIV-Risk Taking Behaviour Scale was administered in written questionnaire form at 2-week intervals (HRBS; [Darke, S., Hall, W., Heather, N., Ward, J., & Wodak, A. (1991). The reliability and validity of a scale to measure HIV risk-taking behaviour among intravenous drug users. AIDS, 5, 181-185]). A mediation analysis was conducted to determine whether abstinence from opiates and cocaine mediated the effect of CM on HRBS scores. Changes in HRBS scores over time differed significantly by treatment (F(9,334)=2.4, p<0.05), with HRBS scores decreasing over time in the CM group to a greater extent than in the noncontingent control group. Participants in the CM group had significantly lower rates of simultaneous cocaine/opiate-positive urine specimens than those in the noncontingent control group during CM treatment (F(1,111)=6.8, p=0.01). The relationship between treatment condition and HRBS scores was mediated by abstinence. CM targeted toward cocaine and heroin use produces significant reductions in injection-related drug-taking behaviors associated with heightened risk for getting or transmitting HIV.