An Invited Updated Systematic Review and Meta-Analysis Comparing Atypical Anorexia Nervosa and Anorexia Nervosa

Since the publication of our earlier systematic review (Walsh et al.), a substantial number of additional studies have examined the psychological and physical characteristics of atypical anorexia nervosa (AN) compared with AN and/or healthy controls. The purpose of the current study was to update and expand the prior systematic review and meta-analysis using newly available data.

A systematic review was conducted in accordance with PRISMA guidelines, including studies from the original review as well as studies published after July 17, 2022 (the final search date of the original review). Eligible studies compared clinical characteristics of individuals with atypical AN to those with AN and/or healthy controls. Meta-analyses were performed when at least three studies reported comparable outcome measures.

Sixty-four publications met criteria for inclusion. Overall, findings indicate that individuals with atypical AN differ demographically from those with AN and demonstrate greater levels of eating disorder-related psychopathology. Non-eating disorder psychopathology is comparable between groups. Individuals with atypical AN experience many of the physiological complications associated with AN, notably menstrual disturbance and decreased bone mineral density, but less frequently.

This updated review confirms and extends findings from the original review, demonstrating that individuals with atypical AN experience substantial psychological distress at levels comparable to those of individuals with AN and similar but less frequent physiological disturbances. These findings continue to support the similarities between atypical AN and AN in clinical and research settings, but underscore the need for specific diagnostic criteria for atypical AN and longitudinal studies to clarify illness course and outcomes.