Relationship between eating disorder duration and treatment outcome: Systematic review and meta-analysis.

OBJECTIVE

This systematic review and meta-analysis examine the contribution of duration to treatment outcome for eating disorders.

METHOD: Studies (n = 31) were identified that examined associations (r) between duration and 45 different outcomes. We were unable to extract r for seven studies (9 outcomes) and extracted r for 36 outcomes across 24 studies (2,349 participants). Indicators of treatment outcome were heterogeneous and thus a series of different meta-analyses, aimed at increasing homogeneity, were conducted.

RESULTS

First, we examined the average effect size for one primary eating disorder related outcome from each of the 24 studies. There was no association between duration and treatment outcome (r = .05, 95% CI: -.03:.13), with high heterogeneity. Second, we conducted three sub-group analyses to explore possible sources of heterogeneity (diagnosis: anorexia nervosa versus bulimia nervosa; nature of the outcome: binary versus continuous; or type of outcome: binary indicator of recovery, eating disorder psychopathology, weight gain). There was no significant moderation or associations between duration and outcome (ranging from .02-.08), with low to medium heterogeneity. Third, two stand-alone analyses examined outcomes related to weight gain (n = 8) and eating disorder psychopathology (n = 5), with nonsignificant rs of .23/-.06, respectively. High levels of heterogeneity were present.

DISCUSSION: Duration did not influence treatment outcome across any of our meta-analyses. Increasing homogeneity and power will allow more stable estimates of the impact of duration on outcome to be calculated; to this end, future treatment studies should include outcome related to weight gain (anorexia nervosa) and improvements in eating disorder psychopathology.