Association of the polygenic risk score for schizophrenia with mortality and suicidal behavior - A Danish population-based study

Background: It is unknown whether an increased genetic liability to schizophrenia influences the risk of dying early. The aim of the study was to determine whether the genetic predisposition to schizophrenia is associated with the risk of dying early and experience a suicide attempt. Method: Case control study, Denmark. The main measure was the mortality rate ratios (MRR) for deaths and odds ratios (OR) for multiple suicide attempts, associated with one standard deviations increase of the polygenic risk-score for schizophrenia (PRS). Results: We replicated the high mortality MRR = 9.01 (95% CI: 3.56-22.80), and high risk of multiple suicide attempts OR = 33.16 (95% CI: 20.97-52.43) associated with schizophrenia compared to the general population. However, there was no effect of the PRS on mortality MRR = 1.00 (95% CI 0.71-1.40) in the case-control setup or in cases only, MRR = 1.05 (95% CI 0.73-1.51). Similar, no association between the PRS and multiple suicide attempts was found in the adjusted models, but in contrast, family history of mental disorders was associated with both outcomes. Conclusions: A genetic predisposition for schizophrenia, measured by PRS, has little influence on the excess mortality or the risk of suicide attempts. In contrast there is a strong significant effect of family history of mental disorders. Our findings could reflect that the common variants detected by recent PRS only explain a small proportion of risk of schizophrenia, and that future, more powerful PRS instruments may be able to predict excess mortality within this disorder. (C) 2016 Elsevier B.V. All rights reserved.