Efficacy of Motivational Interviewing in Treating Co-occurring Psychosis and Substance Use Disorder: A Systematic Review and Meta-Analysis.

A wealth of evidence has supported the efficacy of motivational interviewing (MI) in reducing substance use as well as other addictive behaviors. In view of the common co-occurrence of substance use disorder among individuals with schizophrenia spectrum disorders, there has been increased attention to applying MI in psychological interventions for individuals with co-occurring psychosis and substance use disorder. This review aims to synthesize the evidence on the efficacy of MI interventions (either as a stand-alone intervention or in combination with other psychological interventions) in reducing substance use and psychotic symptoms. MEDLINE, PsycINFO, EMBASE, CENTRAL, and CINAHL were searched using keywords related to "psychosis," "substance addiction," and "motivational interviewing" to identify studies published in English from 1984 to May 2021. Of 1,134 articles identified in the literature, we selected 17 studies for review: 5 studies examined stand-alone MI ("MI-pure"), and 13 studies assessed MI as a major treatment component ("MI-mixed"). Demographics of participants, intervention characteristics, and outcome data were extracted by the first author and checked by the second author. Random-effects models were used for substance use and psychotic symptom outcomes. MI-pure interventions did not significantly reduce severity of substance use ( = 0.06,  = .81) or psychotic symptoms ('s for 2 individual studies = 0.16,  = .54; and 0.01,  = .96). The effect of MI-mixed interventions on substance use decrease was statistically significant but small in size ( = 0.15,  = .048), whereas the effect on psychotic symptom improvement was not significant ( = 0.11,  = .22). With the caveat that only a small number of comparisons were available for the review on MI-pure interventions, the efficacy of MI in treating co-occurring psychosis and substance use disorder was heterogeneous and modest.