Individual gender and group gender composition as predictors of differential benefit from mindfulness-based relapse prevention for substance use disorders.

OBJECTIVES: Mindfulness-based relapse prevention (MBRP) is an effective group-based aftercare treatment for substance use disorders (SUDs), yet few studies have examined moderators of MBRP efficacy. This secondary data analysis evaluated individual gender and group gender composition (e.g., proportion of women relative to men in each therapy group) as treatment moderators of MBRP.

METHODS: The analysis sample included 186 individuals with SUDs randomized to MBRP or relapse prevention (RP) as an aftercare treatment. Outcomes included number of heavy drinking days and drug use days at the 12-month follow-up.

RESULTS: There were no treatment moderation effects for models with heavy drinking days as the outcome (all ps > .05). Group gender composition, but not individual gender, moderated the effect of treatment condition on drug use days (p < .01). Individuals who received MBRP had significantly fewer drug use days at 12-months than those who received RP, but only among individuals in therapy groups comprising one-third or more women (p <0 .0001). Specifically, all women and men who received MBRP in groups with one-third or more women were abstinent from drugs at month 12, whereas those in RP groups with one-third or more women had an average of about eight drug use days at month 12 (corresponding to a large between-treatment condition effect size).

CONCLUSIONS: Group-based MBRP may be more efficacious than group-based RP, particularly when women compose at least one-third of the therapy group. Further research is warranted on gender and group gender composition as moderators of MBRP.