Suicide and all-cause mortality following routine hospital management of self-harm: Propensity score analysis using multicentre cohort data

Background Observational studies are suited to examining links between the routine hospital management of self-harm and future suicide and all-cause mortality due to their large scale. However, care must be taken when attempting to infer causal associations in non-experimental settings. Methods Data from the Multicentre Study of Self-Harm in England were used to examine associations between four types of hospital management (specialist psychosocial assessment, general hospital admission, psychiatric outpatient referral and psychiatric admission) following self-harm and risks of suicide and all-cause mortality in the subsequent 12 months. Missing data were handled by multiple imputation and propensity score (PS) methods were used to address observed differences between patients at baseline. Unadjusted, PS stratified and PS matched risk ratios (RRs) were calculated. Results The PSs balanced the majority of baseline differences between treatment groups. Unadjusted RRs showed that all four treatment types were associated with either increased risks or no change in risks of suicide and all-cause mortality within a year. None of the four types of hospital management were associated with lowered risks of suicide or all-cause mortality following propensity score stratification (psychosocial assessment and medical admission) and propensity score matching (psychiatric outpatient referral and psychiatric admission), though there was no longer an increased risk among people admitted to a psychiatric bed. Individuals who self-cut were at an increased risk of death from any cause following psychosocial assessment and medical admission. Medical admission appeared to be associated with reduced risk of suicide in individuals already receiving outpatient or GP treatment for a psychiatric disorder. Conclusions More intensive forms of hospital management following self-harm appeared to be appropriately allocated to individuals with highest risks of suicide and all-cause mortality. PS adjustment appeared to attenuate only some of the observed increased risks, suggesting that either differences between treatment groups remained, or that some treatments had little impact on reducing subsequent suicide or all-cause mortality risk. These findings are in contrast to some previous studies that have suggested psychosocial assessment by a mental health specialist reduces risk of repeat self-harm. Future observational self-harm studies should consider increasing the number of potential confounding variables collected.