Method of self-harm and risk of self-harm repetition: findings from a national self-harm registry

Background: Risk of self-harm repetition has consistently been shown to be higher following self-cutting compared to intentional drug overdose (IDO) and other self-harm methods. The utility of previous evidence is limited due to the large heterogeneous method categories studied. This study examined risk of hospital presented self-harm repetition according to specific characteristics of self-harm methods. Methods: Data on consecutive self-harm presentations to hospital emergency departments (2010-2016) were obtained from the National Self-Harm Registry Ireland. Associations between self-harm method and repetition were analysed using survival analyses. Results: Overall, 65,690 self-harm presentations were made involving 46,661 individuals. Self-harm methods associated with increased repetition risk included minor self-cutting, severe self-cutting, multiple drug IDOs involving psychotropic drugs and self-harm by blunt object. Minor self-cutting was the method associated with highest repetition risk (adjusted hazard ratio (AHR) 1.38, 95% CI 1.31-1.45). Risk of repetition was comparable following IDOs of four or more drugs involving psychotropic drugs (AHR = 1.29, 95% CI 1.20-1.39), severe self-cutting (AHR 1.25, 95% CI 1.16-1.34) and blunt object (AHR = 1.23, 95% CI 1.07-1.42). Limitations: Information was not available on suicide or other causes of mortality. Conclusions: Self-harm method and the associated risk of repetition should form a core part of biopsychosocial assessments and should inform follow-up care for self-harm patients. The observed differences in repetition associated with specific characteristics of IDO underline the importance of safety planning and monitoring prescribing for people who have engaged in IDO.