Early response to psychological treatment for eating disorders: A systematic review and meta-analysis.

Early response is a well-established predictor of positive outcomes at the end of psychological treatments for common mental disorders. There is some prior evidence that this conclusion also applies to eating disorders, including three meta-analyses, but no moderators of that relationship have been identified. However, a number of further papers have been published since, which might influence the size of the effect of early response or the potential role of moderating factors. This pre-registered systematic review presents a comprehensive examination of this literature. Three databases were searched (Scopus, PsycInfo, PubMed). In total, 33 eligible studies were included in a narrative synthesis, and 25 studies were included in random-effects meta-analysis. The majority (91%) of studies were rated as having low or moderate risk of bias. Approximately half of patients across clinical samples showed early response to psychological therapy, which was most often defined as reliable symptomatic improvement during the first four sessions. A significant and moderate association was found between early response and post-treatment outcomes (r = 0.41 [95% CI: 0.32-0.481], p < .0001). Significant evidence of heterogeneity (Q[28] = 136.42, p < .0001; I2 = 80.2%) was evident. The review was limited by the exclusion of grey literature and only 76% of studies provided sufficient statistical information for meta-analytic synthesis, although we found no significant evidence of publication bias, χ2(1) = 0.001, p = .97. Overall, evidence accumulated over twenty years establishes early response as the most robust predictor of treatment outcomes in the field of eating disorders. However, only half of patients show early change in this way. Further research is needed to determine whether there are patient or clinician characteristics that predict early response to psychological treatment for eating disorders.