Does Pretreatment Severity Moderate the Efficacy of Psychological Treatment of Adult Outpatient Depression? A Meta-Analysis Ellen Driessen VU University Amsterdam and Arkin Mental Health Institute Pim Cuijpers VU University Amsterdam Steven D. Hollon Vanderbilt University Jack J. M. Dekker VU University Amsterdam and Arkin Mental Health Institute Objective: It is widely believed that psychological treatment has little effect on more severely depressed patients. This study assessed whether pretreatment severity moderates psychological treatment outcome relative to controls by means of meta-analyses. Method: We included 132 studies (10,134 participants) from a database of studies (www.evidencebasedpsychotherapies.org) in which the effects of psychological treat- ment on adult outpatients with a depressive disorder or an elevated level of depressive symptoms were compared with a control condition in a randomized controlled trial. Two raters independently extracted outcome data and rated study characteristics. We conducted metaregression analyses assessing whether mean pretreatment depression scores predicted psychological treatment versus control condition posttreatment effect size and subgroup analyses summarizing the results of studies reporting within-study analyses of depression severity and psychological treatment outcome. Results: Psychological treatment was found to be consistently superior to control conditions (d = 0.40 – 0.88). We found no indication that pretreatment mean depression scores predicted psychological treatment versus control condition posttreatment effect size, even after adjusting for relevant study characteristics. However, among the smaller subset of studies that reported within-study severity analyses, posttreatment effect sizes were higher for high-severity patients (d = 0.63) than for low-severity patients (d = 0.22) when psychological treatment was efficacious relative to a more stringent control. Conclusion: Contrary to conventional wisdom, our findings suggest that when compared with control conditions, psychological treatment might be more efficacious for high-severity than for low-severity patients. Because the number of studies reporting within-study severity analyses is small, we recommend that future studies routinely report tests for Severity  Treatment interactions. Keywords: depression, psychological treatment, efficacy, severity, meta-analysis It is widely believed that psychological treatment has little effect on more severely depressed patients. For example, treatment guidelines published by the American Psychiatric Association (2000) suggest that although psychotherapy may be sufficient for patients with less severe depressions, antidepressant medications or electroconvulsive therapy (ECT) is necessary for more severely depressed patients. This belief is based, in part, on the findings of the Treatment of Depression Collaborative Research Program, in which cognitive behavior therapy (CBT) did not separate from placebo in more severely depressed patients but antidepressant medications did (Elkin et al., 1989, 1995). However, what is often overlooked in that study is that interpersonal psychotherapy did separate from placebo among patients with more severe depres- sion, suggesting that psychological treatment can be efficacious in this population. There are two distinct questions that are often confounded in the literature. The first is whether psychological treatment works, and the second is how it compares with other alternative interventions. Whether psychological treatment works is an- swered by comparisons with minimal treatment controls (abso- lute efficacy) or nonspecific controls (specificity), whereas its relative efficacy is determined by comparisons with alternative interventions. In this article, we address the question of whether psychological treatment works, and more specifically, whether the magnitude of this effect (if any) is affected by depression severity. This is a question of moderation that asks whether psychological treatment is more or less likely to differentiate from control conditions as a function of pretreatment severity (Kraemer, Wilson, Fairburn, & Agras, 2002). This study assessed whether pretreatment depression severity is related to psychological treatment outcome compared with control conditions by means of two different meta-analytic techniques: (a) metaregression analyses to assess whether mean pretreatment de- pression scores predict psychological treatment versus control condition posttreatment effect sizes and (b) analyses of studies reporting results of within-study analyses of depression severity and psychological treatment outcome. Ellen Driessen and Jack J. M. Dekker, Faculty of Psychology and Education, Department of Clinical Psychology, VU University Amster- dam, Amsterdam, The Netherlands, and Arkin Mental Health Institute, Amsterdam, The Netherlands; Pim Cuijpers, Faculty of Psychology and Education, Department of Clinical Psychology, VU University Amster- dam; Steven D. Hollon, Department of Psychology, Vanderbilt Univer- sity. Correspondence concerning this article should be addressed to Ellen Driessen, Faculty of Psychology and Education, Department of Clinical Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081 BT, Amsterdam, The Netherlands. E-mail: e.driessen@psy.vu.nl Journal of Consulting and Clinical Psychology © 2010 American Psychological Association 2010, Vol. 78, No. 5, 668 – 680 0022-006X/10/$12.00 DOI: 10.1037/a0020570 668