February 04, 2020
A small but significant increase in the risk for death by suicide occurs in the months immediately following diagnosis of specific neurologic disorders, results of a large, population-based study of more than 7 million individuals show.
Patients diagnosed with a severe neurologic disorder were four to five times more likely to die by suicide compared to the general population. This risk was particularly high among those who had been diagnosed with Huntington disease or amyotrophic lateral sclerosis (ALS).
Although suicide remains a rare event, "neurologists might strive to be attentive towards patients who are distressed at time of diagnosis or who present with symptoms of depression," said study investigator Annette Erlangsen, PhD, head of program at the Danish Research Institute for Suicide Prevention, Mental Health Center, Copenhagen, Denmark.
The study was published online February 4 in JAMA.
Time a Risk Factor
Previous population-based studies have linked suicide with head injury, stroke, epilepsy, and multiple sclerosis. However, the evidence for an association remains "inconclusive" regarding Huntington disease, ALS, and Parkinson disease, owing to study limitations, the investigators note.
Neurologic diagnoses, including meningitis, polyneuropathy, and Guillain-Barre syndrome, are not associated with suicidal behavior, they add, whereas diagnoses of Alzheimer disease and dementia "might be associated with a lower the risk of suicide, although findings have shown inconsistencies."
To get a clearer picture, the researchers analyzed data for more than 7.3 million individuals aged 15 years or older in Denmark for the period 1980–2016. They assessed ICD codes for a wide range of neurologic diagnoses using National Patient Register data.
The dataset included all full-time hospital admissions, outpatient visits, and emergency department consultations in this retrospective cohort study.
During the study period, 35,483 individuals died by suicide. The mean age was 52 years, and almost 15% were living with a neurologic disorder.
Overall, those who had been diagnosed with a neurologic disorder were at significantly higher risk for suicide 44.0 per 100,000 person-years, compared to 20.1 per 100,000 person-years among all other residents of Denmark. The adjusted incidence rate was 1.8.
However, the absolute difference between incidence rates was relatively small: 23.9 per 100,000 person-years.
The researchers report that the highest excess adjusted incidence rate ratios (IRRs) were for Huntington disease, at 4.9 (95% confidence interval [CI], 3.1 – 7.7), and ALS, at 4.9 (95% CI, 3.5 – 6.9).
"We were surprised to see the excess rates associated with ALS and Huntington's disorder," Erlangsen said.
Interestingly, time was a risk factor. Researchers found that suicide risk was highest between the first and third months after diagnosis (adjusted IRR per 100,000 person-years, 3.1; 95% CI, 2.7 – 3.6). In contrast, after 10 or more years, the adjusted IRR was 1.5 (95% CI, 1.4 – 1.6).
Suicide risk was lower for patients with dementia, with an adjusted IRR of 0.8 (95% CI, 0.7 – 0.9), for Alzheimer disease, at 0.2 (95% CI, 0.2 – 0.3), and for those with intellectual disabilities, at 0.6 (95% CI, 0.5 – 0.8).
Timing again made a difference. The adjusted IRR for patients with dementia during the first month after diagnosis was 3.0 (95% CI, 1.9 – 4.6).
"We were intrigued by the finding that people had elevated rates of suicide within the first 3 to 6 months after being diagnosed with dementia," Erlanger said. "However, the rate of suicide declined over time for this group, and after 3 years, they have a lower suicide rate than the general population," said Erlangsen.
The researchers also assessed suicide risk among people with infectious diseases. The adjusted IRR for central nervous system infection was 1.6 (95% CI, 1.3 – 1.9); 1.6 (95% CI, 1.2 – 2.0) for meningitis; and 1.7 (95% CI, 1.3 – 2.3) for encephalitis.
Although findings relating suicide risk to central nervous system infections have been reported, "the results regarding meningitis and encephalitis seem to be novel," the researchers note.
The investigators also found significantly elevated suicide rates associated with Parkinson disorder, polyneuropathy, and Guillain-Barre syndrome, "which have not been shown previously, despite an association of these disorders with mental disorders in other research."
The investigators caution that the study does not show causality. In addition, primary care diagnoses were not included, and therefore it is possible suicide cases were underreported. The strengths of the research include the fact that it was a large population-based study with long-term follow-up.
Going forward, Erlangsen said her team plans to review the findings with clinicians to determine whether certain disorders and specific time points after diagnosis confer greater risk, possibly offering an opportunity for intervention.
Commenting on the findings for Medscape Medical News, Jonathan B. Singer, PhD, LCSW, president of the American Association of Suicidology, said he found it particularly interesting that the study showed increased suicide risk among patients with Huntington's and ALS but not those with dementia and Alzheimer's.
The study results also suggest there is a "need to integrate suicide prevention strategies into the treatment and management of people with Huntington and ALS," added Singer, who also is associate professor of social work at Loyola University Chicago.
The study was supported by a grant from the Psychiatric Research Foundation, Region of Southern Denmark. Erlangsen and Singer have disclosed no relevant financial relationships.