Atypical anorexia nervosa diagnosis should exclude those with lifetime anorexia nervosa: Commentary on Walsh, Hagan, and Lockwood (2022).

Atypical anorexia nervosa (AN) is not well-defined. Walsh, Hagan, and Lockwood (2022) review the data on atypical AN published in the last decade demonstrating overwhelming clinical similarities between atypical AN and AN. As written, atypical AN includes at least three clinical presentations that may not have the same underlying illness, and in turn, may have different prognoses and treatment needs: (1) higher-weight AN; (2) prodromal AN; and (3) partial remission from AN. While useful for the first two presentations, we suggest that the atypical AN diagnosis is not appropriate for those in partial remission from AN. Extant data document symptom fluctuation is part of illness course in AN rather than crossover to a distinct disorder. Further, lifetime AN carries the greatest risk for relapse to low-weight, premature death, and medical morbidities. Finally, emerging data support unique biobehavioral mechanisms in AN suggesting its combination with atypical AN is premature. Therefore, at this time, we recommend that the atypical AN diagnosis be reserved for those without lifetime AN. We encourage research to test and validate operational definitions of atypical AN and partial remission from AN, and further suggest documentation of lifetime AN across the eating disorders given its prognostic value.