Does attrition during follow-up bias outcome data in studies of eating disorders?

Attrition is a pervasive problem in eating disorders research. This study examined whether those who do and do not respond to follow-up assessments differ before or during treatment. Participants (N=268) receiving residential eating disorders treatment were categorized according to those who did ("responders," n=152) and did not ("non-responders," n=116) complete a one-month follow-up assessment. Among participants diagnosed with bulimia nervosa (n=136), responders exhibited significantly higher scores than non-responders at intake on restraint, weight concern, eating concerns, body dissatisfaction, drive for thinness, and depressive symptoms, and had significantly less improvement in eating concerns during treatment. Among participants with anorexia nervosa (n=132), there were no significant differences between responders and non-responders at intake or in treatment improvement. Research on bulimia nervosa treatment based on responders to follow-up assessments may underestimate the amount of improvement that patients experience.