The impact of marijuana use on cocaine use outcomes among patients in methadone maintenance treatment across five trials of contingency management.

Objective: Cocaine use is prevalent among patients in methadone maintenance and a risk factor for poor treatment outcomes. Contingency management (CM) decreases cocaine use in this population, but little is known about its efficacy when marijuana use is present prior to or during treatment.

Method: Data from five randomized CM trials ( = 557) were used to evaluate whether: (a) marijuana frequency (none, low, or high) prior to or during treatment impacts cocaine use outcomes and (b) marijuana use differentially impacts cocaine outcomes with standard care (SC) + CM versus SC alone.

Results: Relative to no marijuana use, low (β = .28, < .01) and high marijuana use (β = .32, < .05) during treatment were associated with roughly 1 week shorter duration of cocaine abstinence on average. Low marijuana use (β = .71, < .05) during treatment was associated with a lower proportion of negative cocaine samples during treatment relative to no marijuana use. Treatment group by marijuana use (before or during treatment) interactions on duration and proportion of cocaine abstinence during treatment were not significant. For longer term outcomes, in SC + CM, marijuana use during treatment did not impact cocaine abstinence 6 months post-baseline. In SC, low (OR = .44, < .05) and high ( = .26, < .001) marijuana use during treatment decreased odds of cocaine abstinence at 6 months post-baseline relative to no use.

Conclusions: Findings highlight the benefits of SC + CM and abstaining from marijuana use during active treatment. At 6 months postbaseline, SC + CM evidenced similar cocaine abstinence regardless of marijuana use levels during treatment, while those with low and high marijuana use showed decreased abstinence rates in SC only. (PsycInfo Database Record (c) 2022 APA, all rights reserved).