A meta-analysis of the effect of therapist experience on outcomes for clients with internalizing disorders.

This meta-analysis synthesized the literature regarding the effect of therapist experience on internalizing client outcomes to evaluate the utility of lay providers in delivering treatment and to inform therapist training. The analysis included 22 studies, contributing 208 effect sizes. Study and client characteristics were coded to examine moderators. We conducted subgroup meta-analyses examining the relationship of therapist experience across a diverse set of internalizing client outcomes. Results demonstrated a small, but significant relationship between therapist experience and internalizing client outcomes. There was no relationship between therapist experience and outcomes in clients with primary anxiety disorders. In samples of clients with primary depressive disorders and in samples of clients with mixed internalizing disorders, there was a significant relationship between experience and outcomes. The relationship between therapist experience and outcomes was stronger when clients were randomized to therapists, treatment was not manualized, and for measures of client satisfaction and "other" outcomes (e.g., dropout). It appears that therapist experience may matter for internalizing clients under certain circumstances, but this relationship is modest. Continuing methodological concerns in the literature are noted, as well as recommendations to address these concerns.