Efficacy of personalized psychological interventions: a systematic review and meta-analysis

Objective: To evaluate the efficacy of different approaches to personalization in psychological therapy. Method: This was a systematic review and meta-analysis of randomized controlled trials that compared the mental health outcomes of personalized treatment with standardized treatment and other control groups. Eligible studies were identified through three databases (Scopus, APA PsycInfo, and Web of Science). We conducted a narrative synthesis and random effects meta-analysis of available outcomes date, including subgroup analyses to investigate sources of effect size heterogeneity. The review protocol was preregistered in the Open Science Framework. Results: Seventeen studies (N = 7,617) met inclusion criteria for the review, nine of which (N = 5,134) provided sufficient data for inclusion in meta-analysis. Eight studies were classed as having high risk of bias, eight had moderate risk, and one had low risk. There was no significant evidence of publication bias. A statistically significant effect size was found in favor of personalized treatment relative to standardized treatment (d = 0.22, 95% CI [0.05, 0.39], p = .011). When studies with a high risk of bias were removed, this effect size was smaller but remained statistically significant (d = 0.14, 95% CI [0.08, 0.20], p < .001). Conclusion: Current evidence indicates that personalization is an effective strategy to improve outcomes from psychological therapy, and the seemingly small effect size advantage of personalization could have an important impact at a clinical population level.