Lifetime prevalence of non-suicidal self-injury in patients with eating disorders: a systematic review and meta-analysis

Background. Against a backdrop of increasing research, clinical and taxonomic attention in non-suicidal self-injury (NSSI), evidence suggests a link between NSSI and eating disorders (ED). The frequency estimates of NSSI in ED vary widely. Little is known about the sources of this variation, and no meta-analysis has quantified the association between ED and NSSI. Method. Using random-effects meta-analyses, meta-regression analyses, and 1816-6466 unique participants with various ED, we estimated the weighted average percentage of individuals with ED, those with anorexia nervosa (AN) and those with bulimia nervosa (BN) who are reported to have a lifetime history of NSSI across studies. We further examined predictors of NSSI in ED. Results. The weighted average percentage of patients with a lifetime history of NSSI was 27.3% [95% confidence interval (CI) 23.8-31.0%] for ED, 21.8% (95% CI 18.5-25.6%) for AN, and 32.7% (95% CI 26.9-39.1%) for BN. The difference between BN and AN was statistically significant [odds ratio (OR) 1.77, 95% CI 1.14-2.77, p = 0.013]. The odds of NSSI increased by 24% for every 10% increase in the percentage of participants with histories of suicide attempts (OR 1.24, 95% CI 1.04-1.48, p = 0.020) and decreased by 26% for every 10% increase in the percentage of participants with histories of substance abuse (OR 0.74, 95% CI 0.58-0.95, p = 0.023). Conclusions. In the specific context of ED, NSSI is highly prevalent and correlates positively with attempted suicide, urging for NSSI-focused treatments. A novel finding is that NSSI is potentially antagonized by substance abuse.