Functional analytic psychotherapy (FAP) is an approach based on contextual behavioral principles with a focus on interpersonal issues. This review quantitatively synthesized the evidence on the efficacy of FAP in addressing various clinical outcomes. A systematic literature search was conducted. After study selection, coding, and data extraction, outcomes were meta-analyzed using a random-effects model. Subgroup analyses, metaregressions, and bias assessments were performed. Seventy studies met the inclusion criteria. Results from single-case designs showed significant improvements in idiographic clinically relevant behaviors (i.e., avoidance of intimacy and conflict vs. engaging in intimacy-promoting behaviors, assertive expression of feelings and needs). Controlled group studies showed robust results for depression and anxiety symptoms. No significant changes were found for anger, experiential avoidance, and mindfulness. Thus, our results provide empirical support for FAP in the treatment of interpersonal behaviors and internalizing symptoms, although bias in the included studies may limit these findings.
