Suicides in degenerative neurocognitive disorders and traumatic brain injuries

Background: Neuropsychiatric symptoms in major neurocognitive disorders have been strongly associated with suicidality. Methods: The objectives were to explore suicide rates in degenerative neurocognitive disorders (DND), alcohol-related neurocognitive disorders (ARND), and traumatic brain injuries (TBI). Patients who received these diagnoses between 1998 and 2015 (N=231,817) were identified from nationwide registers, and their mortality was followed up until Dec 31, 2018. We calculated incidences of suicides per 100 000 person-years, types of suicides, and suicide rates compared with the general population (Standardized Mortality Ratio, SMR). Results: During the follow-up, 0.3% (95% CI: 0.2 to 0.5) of patients with DND, 1.1% (0.7 to 1.8) with ARND, and 1.0% (0.7 to 1.3) with TBI committed suicide. Suicide mortality rate was higher in men 58.9, 51.3 to 67.4 per 100 000 than in women 9.8, 7.5 to 12.5 per 100 000. The highest suicide rate was in ARND (98.8, 65.1 to 143.8 per 100 000), followed by TBI (82.0, 62.4 to 105.8 per 100 000), and DND (21.2, 18.3 to 24.5 per 100 000). The SMRs (95% CI) were 3.69 (2.53 to 5.38), 2.99 (2.31 to 3.86) and 1.31 (1.13 to 1.51), respectively, and no sex difference emerged. The most common cause of death was self-inflicted injury by hanging or drowning (12.4, 10.3 to 14.8 per 100 000). Conclusions: Suicide rates were higher in all three patient groups than the general population. Suicide risk remained elevated for more than ten years after diagnosis. The suicide methods were mostly violent.