Comparisons between atypical anorexia nervosa and anorexia nervosa: Psychological and comorbidity patterns

Objective Literature comparing “atypical” anorexia nervosa (atypical AN) and anorexia nervosa (AN) suggests these diagnoses share significant similarities in eating disorder (ED) pathology and psychiatric comorbidities. This study evaluated potential differences in ED pathology, psychiatric comorbidity, associated mechanisms (i.e., ED fears and perfectionism), and demographic factors (i.e., ethnicity and age) between individuals with atypical AN and AN. Method Data from seven protocols were combined for a total 464 individuals diagnosed with atypical AN (n = 215) or AN (n = 249). Between‐group differences in ED severity and behaviors, psychiatric comorbidities, ED fears, perfectionism, and demographic factors were assessed using t‐tests, Wilcoxon rank‐sum tests, and Fisher's exact test. Results Participants with atypical AN reported higher levels of overvaluation of weight and shape than those with AN. Participants with AN scored higher on food‐related fears (anxiety about eating, food avoidance behaviors, and feared concerns) and fears of social eating, as well as obsessive‐compulsive symptoms. Participants with AN were more likely to identify as Asian or Pacific Islander. No other statistically significant differences were found between groups for overall ED severity, ED behaviors, psychiatric comorbidities, general ED fears, perfectionism, or demographic factors. Discussion Overall, results support previous literature indicating limited differences between individuals with atypical AN and AN, though individuals with atypical AN reported more overvaluation of weight and shape and those with AN reported higher food and social eating fears and obsessive‐compulsive symptoms. Relatively few overall differences between atypical AN and AN highlight the importance of exploring dimensional conceptualizations of AN as an alternative to the current categorical conceptualization. Public Significance This study assessed differences among individuals with atypical anorexia nervosa and anorexia nervosa in eating disorder severity and behaviors, comorbid psychiatric diagnoses, associated mechanisms, and demographic factors. Few differences emerged, though participants with atypical anorexia nervosa reported more overvaluation of weight and shape, while those with anorexia nervosa reported more food and social eating fears and higher obsessive‐compulsive symptoms. Results support exploration of these diagnoses as a spectrum disorder.