Objective: The authors conducted a meta-analytic review of adherence-outcome and competence-outcome findings, and examined plausible moderators of these relations.
Method: A computerized search of the PsycINFO database was conducted. In addition, the reference sections of all obtained studies were examined for any additional relevant articles or review chapters. The literature search identified 36 studies that met the inclusion criteria.
Results: R-type effect size estimates were derived from 32 adherence-outcome and 17 competence-outcome findings. Neither the mean weighted adherence-outcome (r = .02) nor competence-outcome (r = .07) effect size estimates were found to be significantly different from zero. Significant heterogeneity was observed across both the adherence-outcome and competence-outcome effect size estimates, suggesting that the individual studies were not all drawn from the same population. Moderator analyses revealed that larger competence-outcome effect size estimates were associated with studies that either targeted depression or did not control for the influence of the therapeutic alliance.
Conclusions: One explanation for these results is that, among the treatment modalities represented in this review, therapist adherence and competence play little role in determining symptom change. However, given the significant heterogeneity observed across findings, mean effect sizes must be interpreted with caution. Factors that may account for the nonsignificant adherence-outcome and competence-outcome findings reported within many of the studies reviewed are addressed. Finally, the implication of these results and directions for future process research are discussed.
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