Is there an association between neurological disorders and a higher risk of death
by suicide? In this retrospective cohort study that included 7 300 395 persons in
Denmark from 1980 through 2016, there was a significantly higher rate of suicide among
those with a diagnosed neurological disorder than all other persons (44.0 per 100 000
person-years vs 20.1 per 100 000 person-years, adjusted incidence rate ratio, 1.8).
In Denmark, having a diagnosis of a neurological disorder was associated with a small
but statistically significant increased risk of death by suicide. Neurological disorders
have been linked to suicide, but the risk across a broad spectrum of neurological
disorders remains to be assessed. To examine whether people with neurological disorders
die by suicide more often than other people and to assess for temporal associations.
Nationwide, retrospective cohort study on all persons 15 years or older living in
Denmark, from 1980 through 2016 (N = 7 300 395). Medical contact for head injury,
stroke, epilepsy, polyneuropathy, diseases of myoneural junction, Parkinson disease,
multiple sclerosis, central nervous system infections, meningitis, encephalitis, amyotrophic
lateral sclerosis, Huntington disease, dementia, intellectual disability, and other
brain diseases from 1977 through 2016 (n = 1 248 252). Death by suicide during 1980-2016.
Adjusted incidence rate ratio (IRRs) were estimated using Poisson regressions, adjusted
for sociodemographics, comorbidity, psychiatric diagnoses, and self-harm. Of the more
than 7.3 million individuals observed over 161 935 233 person-years (49.1% males),
35 483 died by suicide (median duration of follow-up, 23.6 years; interquartile range,
10.0-37.0 years; mean age, 51.9 years; SD, 17.9 years). Of those, 77.4% were males,
and 14.7% (n = 5141) were diagnosed with a neurological disorder, equivalent to a
suicide rate of 44.0 per 100 000 person-years compared with 20.1 per 100 000 person-years
among individuals not diagnosed with a neurological disorder. People diagnosed with
a neurological disorder had an adjusted IRR of 1.8 (95% CI, 1.7-1.8) compared with
those not diagnosed. The excess adjusted IRRs were 4.9 (95% CI, 3.5-6.9) for amyotrophic
lateral sclerosis, 4.9 (95% CI, 3.1-7.7) for Huntington disease, 2.2 (95% CI, 1.9-2.6)
for multiple sclerosis, 1.7 (95% CI, 1.6-1.7) for head injury, 1.3 (95% CI, 1.2-1.3)
for stroke, and 1.7 (95% CI, 1.6-1.8) for epilepsy. The association varied according
to time since diagnosis with an adjusted IRR for 1 to 3 months of 3.1 (95% CI, 2.7-3.6)
and for 10 or more years, 1.5 (95% CI, 1.4 to 1.6, P < .001). Compared with those
who were not diagnosed with a neurological disorder, those with dementia had a lower
overall adjusted IRR of 0.8 (95% CI, 0.7-0.9), which was elevated during the first
month after diagnosis to 3.0 (95% CI, 1.9-4.6; P < .001). The absolute risk of suicide
for people with Huntington disease was 1.6% (95% CI, 1.0%-2.5%). In Denmark from 1980
through 2016, there was a significantly higher rate of suicide among those with a
diagnosed neurological disorder than persons not diagnosed with a neurological disorder.
However, the absolute risk difference was small. This population epidemiology study
uses Danish registry data to examine associations between neurological disorders and
higher suicide rates from 1980 through 2016.