The Effect of Significant Other Involvement in Treatment for Substance Use Disorders: A Meta-Analysis

Objective: Substantial research has accrued in support of a key role for social processes in substance use disorders (SUD). Researchers have developed a range of interventions that capitalize on these social processes to bolster treatment outcomes by involving significant others (e.g., romantic partners, family, friends) in SUD treatment. Yet dissemination of these treatments to many contexts has been slow, and information on their broad efficacy is lacking. This meta-analysis aims to quantify the effect of significant other involvement in SUD treatments above and beyond individually-based therapies. Method: A total of 4,901 records were screened for randomized controlled trials examining the effect of Significant Other Involved SUD Treatments (SOIT) versus individually-based active comparator treatments. Our search yielded 77 effect sizes based on data from 2,115 individuals enrolled in 16 independent trials. Results: Findings indicated a significant effect of SOIT above and beyond individually-based active comparator treatments for reducing substance use and substance-related problems, d 0.242, 95% CI [0.148, 0.336], I 2 10.596, Q(15) 16.778. This effect was consistent across SOIT treatment types and endured 12–18 months after the end of treatment. Analyses of raw mean differences indicated that this effect translates to a 5.7% reduction in substance use frequency—the equivalent of approximately 3 fewer weeks a year of drinking/drug use. Conclusion: Findings indicate a significant advantage for SOIT in SUD treatment, and hold interesting conceptual implications for theories of SUD maintenance.