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Suicide more common in individuals with high systemic inflammation

Individuals with increased levels of inflammation were four times more likely to complete suicide, compared with those with lower levels.

“In psychiatric patients, inflammation is positively associated with the intensity of self-reported suicidal ideation, and those who commit suicide have higher cytokine levels post mortem relative to control patients. Furthermore, individuals with asthma, a condition characterized by inflammation, experience higher rates of suicide mortality than their nonatopic counterparts,” G. David Batty, DSc, of University College London, and colleagues wrote. “While these various lines of evidence may implicate inflammation in the pathophysiology of suicide, there has been no prospective examination of the link between inflammation and future suicide events.”

To assess associations between systemic inflammation and risk for completed suicide within the general population, researchers pooled data from a series of independent, geographically representative surveys of individuals living in private households from January 1998 to May 2007 in the United Kingdom. Analysis included 39,349 individuals with data for inflammation, age, sex and mortality. Participants had a mean follow-up duration of 8.6 years.

During follow-up, there were 26 completed suicides or 7.7 events per 100,000 person-years.

Analysis adjusted for age and sex indicated being a cigarette smoker (adjusted HR = 9.67; 95% CI, 3.82-24.52), male (aHR = 2.64; 95% CI, 1.15-6.07), socioeconomically disadvantaged (aHR = 4.02; 95% CI, 1.6-10.13) and psychologically distressed (aHR = 4.89; 95% CI, 2.22-10.8) were associated with increased rates of suicide.

Individuals in the highest inflammation group were four times more likely to die by suicide, compared with those in the lowest group (HR = 4.2; 95% CI, 1.44-12.25).

Findings were not significantly different when excluding individuals with high thresholds of C-reactive protein (ie, 4, 6, 8, and 10 mg/L), according to researchers.

“This is the first prospective cohort study to examine the link between systemic inflammation and future suicide risk, but it is not without its shortcomings. Despite a large sample size, the number of completed suicides herein was modest, leading to low statistical power. Our results warrant testing using the present study design and other approaches, such as mendelian randomization and large-scale pharmacological trials of inflammation reduction,” the researchers concluded. – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.