Exploring characteristics and risk of repetition in people who fail to report previous hospital presentations for self-harm: A case-control study using data from The Manchester Self-Harm Project

Background: As a risk factor for future self-harm and suicide, questions about past self-harm are typically included in assessments that help inform management of people who self-harm. However, little is known about people with a history of self-harm who do not report it. This study aimed to describe and compare (i) characteristics of people who did or did not accurately report previous self-harm, and (ii) 12-month repetition of self-harm. Methods: Data on all self-harm presentations to three hospital emergency departments in England were collected from 2003 to 2015. A 1:5 matched case-control design included 374 cases where previous self-harm was not reported and 1,870 controls where previous self-harm was reported. Data were analysed using conditional logistic regression and survival analysis. Results: Cases were more likely to be male (OR 1.42; 95% CI 1.13-1.77), middle-aged (OR 1.41; 95% CI 1.08-1.83), employed (OR 1.51; 95% CI 1.15-1.98), and less likely be referred to psychiatric services (OR 0.53; 95% CI 0.35-0.80). Twelve-month repetition was similar in cases and controls (30% vs 31%). Limitations: Self-harm not resulting in a hospital presentation could not be verified and individuals with a single episode in the study database were therefore excluded. Conclusions: Previous self-harm is an important risk factor for repetition in people who accurately recall and report it and those who fail to report it. Those who do not report previous self-harm are less likely to be referred to psychiatric services, emphasising the need for careful assessment of every self-harm presentation to emergency departments.