Motivational Interviewing-Based Compliance/Adherence Therapy Interventions to Improve Psychiatric Symptoms of People With Severe Mental Illness: Meta-Analysis.

Background: Nonadherence is the leading cause of relapse in mental illness. No quantitative synthesis of multiple studies has been conducted to determine the effect of motivational interviewing (MI)-based compliance/adherence therapy (CAT) interventions on people with severe mental illness.

Objective: To synthesize the studies that examined the effectiveness of MI-based CAT interventions to improve psychiatric symptoms.

Design: Quantitative meta-analysis.

Results: Sixteen primary studies were retrieved ( N =1267 participants). MI-based CAT interventions significantly improved psychiatric symptoms with a moderate effect size (ES) of .45. Longer sessions and higher intervention doses showed significantly greater ESs than shorter sessions and lower doses. ESs were significantly lower when participants were older and when there was a longer period between the intervention and outcome measurement.

Conclusions: These findings support the effectiveness of MI-based CAT interventions. Session length and dose effect should be considered when tailoring MI to clients.