Does cannabis use predict poor outcome for heroin-dependent patients on maintenance treatment? Past findings and more evidence against

Abstract

Aims: To determine whether cannabinoid-positive urine specimens in heroin-dependent out-patients predict other drug use or impairments in psychosocial functioning, and whether such outcomes are better predicted by cannabis-use disorders than by cannabis use itself.

Design: Retrospective analyses of three clinical trials; each included a behavioral intervention (contingency management) for cocaine or heroin use during methadone maintenance. Trials lasted 25-29 weeks; follow-up evaluations occurred 3, 6 and 12 months post-treatment. For the present analyses, data were pooled across trials where appropriate.

Setting: Urban out-patient methadone clinic.

Participants: Four hundred and eight polydrug abusers meeting methadone-maintenance criteria.

Measurements: Participants were categorized as non-users, occasional users or frequent users of cannabis based on thrice-weekly qualitative urinalyses. Cannabis-use disorders were assessed with the Diagnostic Interview Schedule III-R. Outcome measures included proportion of cocaine- and opiate-positive urines and the Addiction Severity Index (at intake and follow-ups).

Findings: Cannabis use was not associated with retention, use of cocaine or heroin, or any other outcome measure during or after treatment. Our analyses had a power of 0.95 to detect an r2 of 0.11 between cannabis use and heroin or cocaine use; the r2 we detected was less than 0.03 and non-significant. A previous finding, that cannabis use predicted lapse to heroin use in heroin-abstinent patients, did not replicate in our sample. However, cannabis-use disorders were associated weakly with psychosocial problems at post-treatment follow-up.

Conclusions: Cannabinoid-positive urines need not be a major focus of clinical attention during treatment for opiate dependence, unless patients report symptoms of cannabis-use disorders.

Figure 1

Mean (SEM) percentages of urine specimens negative for the targeted drug (illicit opiates or cocaine) during the Baseline (B), Intervention (I), and maintenance (M) phase of each study. Vouchers were available during the Intervention phase only. Data are shown only for participants whose voucher earnings were contingent on abstinence, not for control participants who received vouchers noncontingently. For the Intervention and Maintenance phases, repeated-measures ANCOVAs controlling for Baseline use of the targeted drug showed no main effect of cannabis-use category and no interaction of cannabis-use category with time.