Non‐suicidal self‐injury among individuals with an eating disorder: A systematic review and prevalence meta‐analysis

OBJECTIVE: This study aimed to quantify the prevalence of non-suicidal self-injury across eating disorders (EDs) and within diagnostic categories through systematic review and proportional, or so-called prevalence, meta-analysis. METHOD: Included studies had to contain individuals with a verified diagnosis of an ED. The last literature search was conducted on September 11, 2023, for studies published on or before September 2023 without a restriction on earliest publication year. Results were synthesized and analyzed using the "metaprop" package in R and presented using forest plots. Bias was assessed by a Peters' regression test and funnel plot. RESULTS: 79 studies published between 1985 and 2023 were included encompassing 32,334 individuals with an ED. Importantly, 42 studies were not included in any other meta-analyses on self-injury in EDs to date. Overall prevalence of non-suicidal self-injury was 34.59% (95%CI = 30.49-38.81). Prevalence in anorexia nervosa restrictive type, binge/purge type, bulimia nervosa, binge eating disorder and other specified feeding/eating disorder were 23.19% (95%CI = 16.96-30.03%), 41.98% (95%CI = 32.35-51.91%), 36.97% (95%CI = 30.69-43.46%), 21.21% (95%CI = 14.93-28.12%) and 37.65% (95%CI = 28.59-47.09%), respectively. Prevalence estimations could not be estimated for other ED categories due to lack of a sufficient number of studies. DISCUSSION: Non-suicidal self-injury is prevalent across both binge/purge and restrictive EDs. Considering the transdiagnostic nature of self-injurious behaviors in ED, the results highlight the importance of assessment and monitoring of self-injury in people with ED, irrespective of specific diagnoses. The method of determining self-injury varied across studies and may limit this study. PUBLIC SIGNIFICANCE: This study highlights the prevalence of self-injury across eating disorders irrespective of diagnosis and within specific EDs. While diagnoses known to exhibit self-injurious behaviors (e.g., bulimia nervosa, anorexia nervosa binge/purge subtype) demonstrated the highest prevalence of self-injury, all diagnoses were found to have a prevalence greater than 20%. These findings suggest the importance of assessing and monitoring all individuals with an eating disorder for the presence of self-injury.