Lauren N. Forrest

Objective Little is known about how individuals with atypical anorexia nervosa (AN) respond to eating disorder (ED) treatment in a partial hospitalization program (PHP), nor how certain factors such as trauma, childhood abuse, psychiatric comorbidity, and suicidal thoughts and behaviors might contribute to poor treatment outcomes. Thus, the current study (1) compares prevalence of these factors between individuals with AN and atypical AN upon admission to an ED PHP, (2) compares PHP treatment response between groups, and (3) investigates whether experiencing these factors impacts treatment outcomes. Method We conducted a retrospective chart review of young adults admitted to a PHP with AN ( n = 95) and atypical AN ( n = 59). Histories of psychiatric comorbidities and adverse childhood experiences were obtained from initial psychiatric evaluations. ED symptoms were assessed at intake and discharge with the Eating Disorder Examination‐Questionnaire (EDE‐Q). Results No significant differences were found at intake in ED symptom severity or prevalence of lifetime trauma, childhood abuse, number of psychiatric diagnoses, or suicidal thoughts and behavior. Symptomatology at discharge also did not differ between groups. Emotional abuse was significantly related to discharge shape and weight overvaluation. No other intake characteristics were significantly related to discharge symptomatology. Discussion To our knowledge, this is the first study to compare the prevalence of comorbidities for both AN and atypical AN, as well as differential treatment outcomes for these individuals in a PHP. Results add to growing literature suggesting that, other than weight, AN and atypical AN have few properties that reliably distinguish them from one another. Public Significance This study adds to a growing body of literature that raises questions about whether anorexia nervosa (AN) and atypical AN are truly different diagnoses. Our findings suggest these two groups present to treatment in a partial hospitalization program (PHP) with similar ED symptoms, as well as prevalence of lifetime trauma, childhood abuse, suicidal thoughts and behavior, and number of psychiatric comorbidities, and demonstrate similar treatment trajectories in PHP.