Premature discontinuation from therapy is a widespread problem that impedes the delivery of otherwise effective psychological interventions. The most recent comprehensive review found an average dropout rate of 47% across 125 studies (Wierzbicki & Pekarik, 1993); however, given a number of changes in the field over the past 2 decades, an updated meta-analysis is needed to examine the current phenomenon of therapy dropout. A series of meta-analyses and meta-regressions were conducted in order to identify the rate at which treatment dropout occurs and predictors of its occurrence. This review included 669 studies representing 83,834 clients. Averaging across studies using a random effects model, the weighted dropout rate was 19.7%, 95% CI [18.7%, 20.7%]. Further analyses, also using random effects models, indicated that the overall dropout rate was moderated by client diagnosis and age, provider experience level, setting for the intervention, definition of dropout, type of study (efficacy vs. effectiveness), and other design variables. Dropout was not moderated by orientation of therapy, whether treatment was provided in an individual or group format, and a number of client demographic variables. Although premature discontinuation is occurring at a lower rate than what was estimated 20 years ago (Wierzbicki & Pekarik, 1993), it is still a significant problem, with about 1 in every 5 clients dropping out of therapy. Special efforts should be made to decrease premature discontinuation, particularly with clients who are younger, have a personality or eating disorder diagnosis, and are seen by trainee clinicians. © 2012 American Psychological Association
