The absolute risk difference is small, but statistically significant. “These findings do not necessarily warrant changing the management of treatment for individual patients,” wrote, a researcher at the Danish Research Institute for Suicide Prevention in Hellerup, and colleagues. “As with all patients, physicians should be aware of the potential for depression, demoralization, and suicide.”
In addition, dementia, Alzheimer’s disease, and intellectual disabilities may be associated with lower suicide rates, according to the study, which was published in.
“Plausible mechanisms” could underlie the association between neurologic disease and suicide, the authors wrote. A neurologic diagnosis “may constitute a distressing life event,” and the diseases may have psychological, physical, and psychiatric effects. Patients may see themselves as a burden or have less financial security. In addition, the diseases may entail “communication difficulties, poor sleep, and pain.” Neurologic diseases may alter brain circuitry and functioning and influence aggression and impulsivity. “People with neurologic disorders may also have easier access to toxic medication,” they added.
More than a dozen conditions examined
Prior studies have found associations between neurologic conditions and rates of suicide, but data have been inconclusive or inconsistent for some of the disorders. To examine whether people with neurologic disorders have higher suicide rates, relative to people without these disorders, the researchers conducted a retrospective study. They analyzed data from more than 7.3 million people aged 15 years or older who lived in Denmark between 1980 and 2016. The cohort included more than 1.2 million people with neurologic disorders. The investigators identified neurologic disorders using ICD codes for head injury, stroke, epilepsy, polyneuropathy, diseases of the myoneural junction, Parkinson’s disease, multiple sclerosis, CNS infections, meningitis, encephalitis, amyotrophic lateral sclerosis, Huntington’s disease, dementia, intellectual disability, and other brain disorders. They compared incidence rates using a Poisson regression model and adjusted for time period, sex, age, region, socioeconomic status, comorbidity, self-harm or psychiatric hospitalization prior to a neurologic diagnosis, and whether a person lived alone.
In all, 35,483 people in the cohort died by suicide at an average age of about 52 years; 77.4% were male. About 15% of those who died by suicide had a neurologic disorder. The suicide incidence rate among people with a neurologic disorder was 44.0 per 100,000 person-years, whereas the rate among people without a neurologic disorder was 20.1 per 100,000 person-years.
The adjusted incidence rate ratio for people with a neurologic disorder was 1.8. The rate ratio was highest during the 3 months after diagnosis, at 3.1. Huntington’s disease and amyotrophic lateral sclerosis were associated with “the largest excess adjusted [incidence rate ratios] of suicide mortality,” with a rate ratio of 4.9 for each condition, the researchers reported. The adjusted incidence rate ratio was 1.7 for head injury, 1.3 for stroke, 1.7 for epilepsy, 1.4 for intracerebral hemorrhage, 1.3 for cerebral infarction, 1.3 for subarachnoid hemorrhage, 1.7 for polyneuropathy and peripheral neuropathy, 2.2 for Guillain-Barré syndrome, 1.9 for diseases of myoneural junction and muscle, 1.8 for other brain disorders, 1.7 for Parkinson’s disease, 2.2 for multiple sclerosis, and 1.6 for CNS infection.
Compared with people without a neurologic condition, people with dementia, Alzheimer’s disease, and intellectual disabilities had lower suicide rates, with adjusted incidence rate ratios of 0.8, 0.2, and 0.6, respectively. “However, the adjusted [incidence rate ratio] for people with dementia during the first month after diagnosis was 3.0,” the researchers wrote.
In addition, the suicide rate increased with an increasing cumulative number of hospital contacts for neurologic conditions.