Risks and familial coaggregation of death by suicide, accidental death and major psychiatric disorders in first-degree relatives of individuals who died by suicide

Background Evidence suggests a familial coaggregation of major psychiatric disorders, including schizophrenia, bipolar disorder, major depression (MDD), autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). Those disorders are further related to suicide and accidental death. However, whether death by suicide may coaggregate with accidental death and major psychiatric disorders within families remains unclear. Aims To clarify the familial coaggregation of deaths by suicide with accidental death and five major psychiatric disorders. Method Using a database linked to the entire Taiwanese population, 68 214 first-degree relatives of individuals who died by suicide between 2003 and 2017 and 272 856 age- and gender-matched controls were assessed for the risks of death by suicide, accidental death and major psychiatric disorders. Results A Poisson regression model showed that the first-degree relatives of individuals who died by suicide were more likely to die by suicide (relative risk RR = 4.61, 95% CI 4.02-5.29) or accident (RR = 1.62, 95% CI 1.43-1.84) or to be diagnosed with schizophrenia (RR = 1.53, 95% CI 1.40-1.66), bipolar disorder (RR = 1.99, 95% CI 1.83-2.16), MDD (RR = 1.98, 95% CI 1.89-2.08) or ADHD (RR = 1.34, 95% CI 1.24-1.44). Conclusions Our findings identified a familial coaggregation of death by suicide with accidental death, schizophrenia, major affective disorders and ADHD. Further studies would be required to elucidate the pathological mechanisms underlying this coaggregation.