Does response to treatment differ between anorexia nervosa and atypical anorexia nervosa? Findings from two open series trials

Background: No evidence-based treatments exist for atypical anorexia nervosa (AAN) and little is known about differences in response to treatment between anorexia nervosa (AN) and AAN. The purpose of this paper is to explore treatment outcomes in two pilot trials for those with AN and AAN. Methods: Study 1 (N N = 127) examined treatment outcomes in a digital imaginal exposure trial and Study 2 (N N = 34) examined outcomes in a personalized treatment trial. Participants with an active eating disorder (ED) were eligible and those with AN or AAN were included in these analyses. ED symptoms and ED-related fears were assessed at pre-treatment, post-treatment, and one and six-month follow-up. Linear mixed effects models explored treatment outcomes by diagnosis. Results: There were no significant differences in treatment response between diagnoses for most outcome measures. In Study 2, participants with AAN had a significant decrease in global ED symptoms across time, while AN did not. Limitations: The samples were primarily white and female, limiting the generalizability of the studies. Additionally, due to limited consensus on "significant weight loss," a less conservative definition was used to diagnose AAN which may impact the results. Conclusions: In general, those with AN and AAN may respond to treatment similarly, with some small differences. Digital exposure therapy may be effective treatments for both AN and AAN, especially for ED-related fears. Personalized treatment may be more effective for those with AAN than those with AN.