group drug counseling. In addition, one arm received individual drug counseling, one received cognitive therapy, and one received supportive expressive therapy. Outcomes were measured using the Addiction Severity Index, a drug use score, and the number of days of cocaine use in the past month. Outcomes were assessed monthly during treatment period, and at 9, 12, 15, and 18 months after randomization. The best results were found for the group drug counseling+individual drug counseling group. The study and its presentation are noteworthy for the attention paid to protocol violations, with follow-up of violators, analyses of missing data and treatment integrity, assessment of possible unique therapist effects, and so on.
S.T.Higgins et al. (1995) Outpatient behavioral treatment for cocaine dependence: One-year outcome. Experimental and Clinical Psy chopharmacology 3:205–212. This study analyzes 12-month follow-up data from two randomized controlled trials, involving a total of 78 community residents who met DSM-III-R criteria for cocaine dependence. Both trials compared traditional drug abuse counseling to a community reinforcement approach involving spouses, friends, or relatives and employment and other counseling services, and an incentive voucher system in which participants earned retail vouchers of modest monetary value for each negative urinalysis over a 24-week period. The first trial compared traditional counseling and the community reinforcement approach+vouchers; the second compared the community reinforcement approach alone to community reinforcement approach+vouchers. Outcomes included the Addiction Severity Index and urine test results. All conditions showed significant improvement over the course of the trials; community reinforcement approach+vouchers was superior to traditional counseling on various outcome measures, but the community reinforcement approach alone and community reinforcement approach+vouchers did not significantly differ from each other. The authors acknowledge that the small sample size provided adequate statistical power for within-treatment effects but inadequate power for post-treatment follow-up results.
K.Silverman, S.T.Higgins, R.K.Brooner, I.D.Montoya, E.J. Cone, C.R.Schuster, and K.L.Preston (1996) Sustained cocaine abstinence in methadone maintenance patients through voucher-based reinforcement therapy. Archives of General Psychiatry 53:409–415. This study usefully complements the Higgins et al. study cited above, extending that research in two ways. First, this study examined the effects of a similar voucher-based treatment for cocaine use, but among heroin abusers in a methadone maintenance program rather than community volunteers. Second, this study compared the contingent voucher program to a control condition in which participants were yoked to members of the treatment group; these latter participants thus received vouchers that were not con-