Incremental validity of weight suppression in predicting clinical impairment in bulimic syndromes.

Research has shown that weight suppression (WS; the difference between a person's highest and current body weight in pounds) is a robust predictor of weight gain and eating-disorder (ED) symptoms among individuals with bulimic syndromes. Given the important prognostic role that WS plays in ED course and outcome, we hypothesized that WS would represent a clinically useful indicator of impairment for bulimic syndromes. We further posited that WS would demonstrate incremental validity above-and-beyond other proposed indicators in explaining clinical impairment in bulimic syndromes. Participants were community-recruited adults (N = 101; 80.2% female) with full-threshold (n = 51) or subthreshold (n = 50) bulimia nervosa. Other indicators of impairment included body mass index, frequency of inappropriate compensatory behaviors, lifetime history of any internalizing disorder, and multiple purging. Clinical impairment was assessed with the clinical impairment assessment (CIA). Hierarchical linear regression tested whether WS added to the explanation of CIA score variance above-and-beyond other indicators of bulimic-syndrome impairment. WS was significantly associated with clinical impairment (p = .011), but did not demonstrate incremental validity over other independent variables in predicting CIA scores. WS explained an additional 1.7% of the variance in CIA scores above-and-beyond other variables and the independent effect of WS on CIA scores represented a medium-sized effect (Cohen's d = 0.521). Results suggested that WS may be an indicator of ED-related clinical impairment. Inquiring about WS could be an informative component of routine bulimic-syndrome assessment, given that WS explains some of the variance in clinical impairment in bulimic syndromes.