Hospital treated deliberate self-harm: mortality risk and area level associations – a national registry cohort study

Introduction Suicide is a major public health problem. Suicide is hard to predict, however research has identified that deliberate self-harm is the strongest predictor for future suicide. The magnitude of the risk of suicide and non-suicide external causes of death (mainly poisonings, falls and road traffic accidents) in the period following a hospital presentation with self-harm, has not been well estimated in representative samples of well-defined patients. Furthermore, to better understand the causes of suicidal behaviour the characteristics of the areas in which people reside need to be examined also. An ecological perspective on suicidal behaviours examines how area level characteristics such as socioeconomic deprivation and social fragmentation influence small area rates of deliberate self-harm and suicide. The main aims of this thesis are to examine the risk of suicide and non-suicide external cause mortality in a cohort of individuals who have presented to hospital due to self-harm in the Republic of Ireland. Additionally, the ecological relationship between suicidal behaviour (both self-harm and suicide) and area level determinants in the Republic of Ireland will be examined. Methods To identify mortality due to external causes among the self-harm patient cohort, the National Registry of Deliberate Self Harm Ireland data (for the years 2009-2011) was linked using probabilistic data linkage techniques to official external cause mortality data (for the years 2009-2011). Separate negative binomial regression models were used to examine the relationship between deliberate self-harm and area level determinants and suicide and area level determinants. Results Findings from the linkage study showed that 437 of 26,168 self-harm patients died from external causes during the study follow-up. The 1-year cumulative incidence for suicide, non-suicide external cause mortality and all external causes combined were 0.8% (95%CI 0.7-0.1), 0.5% (95%CI 0.4-0.6) and 1.3% (95%CI 1.2-1.5), respectively. The risk of suicide was 46 times (95% CI 39-54) greater in self-harm population compared to the general population. The risk of non-suicide external cause mortality was 22 times greater (95% CI 18-27) in the self-harm population compared to the general population. Findings from the self-harm area-level study showed that socioeconomic deprivation, social fragmentation and population density had a positive linear association with self-harm, with socioeconomic deprivation having the strongest independent effect. Findings from the suicide area-level study showed that socioeconomic deprivation had the strongest independent effect on small-area rates of suicide. Discussion The findings of this thesis show the extremely high risk of death from suicide and non-suicide external causes following hospital presentation with self-harm. Furthermore, this thesis demonstrates the marked geographical inequalities in the distribution of both suicide and self-harm in Ireland and highlights the importance of targeting suicide prevention resources in the most deprived areas