Abstract
OBJECTIVE: Currently, there is debate in the eating disorders field regarding how to define atypical anorexia (AAN), how prevalent it is in community and clinical settings, and how AAN rates compare with low-weight AN. This systematic review assesses AAN literature from 2007 to 2020, to investigate: (a) the demographic characteristics of AAN studies, (b) the prevalence of AAN compared with AN, (c) the range of operational definitions of AAN and the implications of these definitions, and (d) the proportion of patients with AAN and AN represented in consecutive admission and referral samples. METHOD: PsychINFO, CINAHL, PubMed, Greylit.org, and ProQuest databases were searched according to methods for Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic reviews, yielding 3,184 potential articles. Seventy-five eligible studies were coded for sixty-one variables. RESULTS: Clinical samples predominantly included younger, female, white samples with limited diversity. In epidemiological designs, AAN was typically as common or more common than AN, and AAN rates varied significantly based on the population studied and operational definitions. In consecutive clinical samples, AAN was frequently less represented. DISCUSSION: Although AAN appears to occur more frequently than AN in communities, fewer patients with AAN are being referred and admitted to eating disorder specific care, particularly in the United States. Given the significant medical and psychosocial consequences of AAN, and the importance of early intervention, this represents a crucial treatment gap. Additionally, results suggest the need for fine-tuning diagnostic definitions, greater diversity in AAN studies, and increased screening and referral for this vulnerable population.