Risk of self-harm in patients with eating disorders: English population-based national record-linkage study, 1999-2021.

OBJECTIVE: Anorexia nervosa (AN) and bulimia nervosa (BN) are eating disorders associated with high rates of self-harm (SH). This is the first national study in England to quantify this association in a hospital population. METHOD: A retrospective cohort study using a linked national dataset of Hospital Episode Statistics for 1999-2021. The exposure cohort included individuals aged <35 years admitted to hospital with a diagnosis of AN or BN. The reference cohort included hospital controls. We calculated the rate ratio (RR) of SH in each cohort. The individuals in the two cohorts were matched on multiple socio-demographic indicators. The main outcome was a subsequent hospitalization or death record with an SH diagnosis. RESULTS: We identified 15,004 females and 1411 males with AN, and 6055 females and 741 males with BN. The RR with 95% confidence intervals (95%CI) for a subsequent admission with intentional self-harm after admission with AN was 4.9 (95%CI 4.7-5.1) in females and 4.8 (95%CI 3.9-5.8) in males. For BN it was 9.0 (95%CI 8.4-9.6) in females and 9.8 (95%CI 7.7-12.2) in males. There were strong associations between AN and BN and other SH. DISCUSSION: Women and men admitted to English hospitals with AN or BN have a very high risk of a subsequent admission with SH. For some SH behaviors, such as alcohol intoxication, the RR was >10-fold elevated. The magnitude of risk was higher for BN than for AN. Clinicians should be aware of the scale of risk increase. Providing those at risk with appropriate support is required. PUBLIC SIGNIFICANCE: This study is the first national study in an English hospital population that confirms and quantifies the association between eating disorders and self-harm. We have found that both women and men admitted to hospital with anorexia nervosa or bulimia nervosa are at an increased risk of subsequent admission with self-harm. It is important that clinicians are aware of this increased risk to support those at highest risk of self-harm.