The efficacy of personalization within psychological treatments compared to no or less personalization: A meta-analysis and systematic review.

Objective: This meta-analysis and systematic review assessed whether personalization within psychological treatments for mental health problems or persistent somatic symptoms improves treatment outcomes, compared to non- or less personalized treatments.

Method: APA PsycInfo, Cochrane Library, MEDLINE, and EMBASE were searched up to January 14, 2024, for randomized controlled trials comparing within-treatment personalization against no or less personalization. Risk of bias was assessed with the Cochrane tool. A meta-analysis was performed using a random-effects model. Additionally, a three-level meta-analysis was conducted, and moderation analyses were performed. A narrative synthesis was included.

Results: Sixteen studies were included. Risk of bias was low for two studies and high for three studies, and 11 studies had some concerns. Effect sizes were calculated for the subgroups: symptoms, smoking cessation, and treatment process outcomes. For symptoms, the pooled standardized mean difference was 0.07 (95% CI [-0.06, 0.20], p = .28); for smoking cessation, the pooled odds ratio was 1.12 (95% CI [0.84, 1.51], p = .43); and for treatment process outcomes, the pooled standardized mean difference was 0.29 (95% CI [-0.27, 0.85], p = .31). Treatment format (in person/online), personalization factor (preference/individual profile), or personalized treatment aspect (content/modules) did not moderate the effect of personalization.

Conclusions: Evidence of moderate quality does not convincingly suggest that within-treatment personalization outperforms no or less personalization with respect to treatment outcome. Using evidence-based personalization strategies, future studies should clarify which degree of personalization yields clinically relevant effects for which populations, interventions, and outcomes. (PsycInfo Database Record (c) 2025 APA, all rights reserved).