Background Suicide is a major public health problem. The prediction of suicide is difficult, however research has identified that deliberate self-harm (DSH) is one of the strongest predictors of future suicide. To date, the risk of suicide in individuals who DSH is not well established internationally as relatively few countries have accurate data on DSH. This is the first registry based study to examine the risk of mortality on a national cohort of all individuals presenting to hospital due to DSH in Ireland.

Methods A national prospective cohort of 26,168 DSH patients attending the 40 hospital emergency departments in Ireland from 2009 to 2011, were followed up until to the end of 2011 using national death recording systems. Gender specific age adjusted European standardised rates for external cause mortality were calculated. Additionally, Poisson regression was used to generate incidence rate ratios (IRRs). Potential risk factors were investigated using Cox Models.

Results During the study follow-up 437 patients died from external causes. The average 1 year cumulative incidence for suicide, non-suicide external cause mortality and all external causes combined were 0.8%, 0.5% and 1.3% respectively. The risk of suicide within the first year after DSH was 46 times greater in DSH population compared to the general population. Risk of other non-suicide external cause mortality was also greater in the DSH population compared to the general population (females; IRR=30, males; IRR=20). While the relative risk of death was higher in the female DSH population compared to the female general population, the absolute risk of death was found to be higher in males than females. Older age and male gender were associated with an elevated risk of death. Risk of death from suicide varied depending on method of DSH. Compared with overdose alone attempted hanging had the greatest risk of suicide, particularly in females (females; HR=6.8, males; HR=2.6), major self-cutting was also associated with a 2-fold increased risk. DSH repetition was also found to be a strong predictor of subsequent death.

Conclusion The findings from the world’s first national DSH Registry highlight the extremely high risk of death from suicide and other external causes following hospital treated DSH. Older age, male gender, DSH repetition (especially for females) and persons presenting with attempted hanging or major self-cutting are at a particular risk. The findings from this study highlight the need for well-structured, specialist and organised care for this vulnerable group attending emergency departments.