Infection, inflammation tied to higher suicide risk

Last Updated: 2016-08-16

By David Douglas

NEW YORK (Reuters Health) - Systemic inflammation and hospitalization for infection both appear to be associated with a higher suicide risk, according to two new studies.

"We were surprised to find an elevated suicide risk for almost any infection," Helene Lund-Sørensen, a medical student at the University of Copenhagen, Denmark, who worked on one of the studies, told Reuters Health by email.

"Although both viral and bacterial infections were linked to an excess risk," she added, "we did find that the excess risk decreases over time since last hospitalization with treatment for infections."

Both papers were published online August 10 in JAMA Psychiatry.

Lund-Sørensen and colleagues examined Danish national data on more than 7.2 million people followed for 32 years starting in 1980. During follow-up, more than 809,000 were hospitalized with infection and there were more than 32,000 suicides.

Nearly a quarter of those who committed suicide had previously been diagnosed with an infection during a hospital stay. Such hospitalization was linked to a significantly higher risk of suicide (independent risk ratio, 1.42).

The more infections and the longer the treatment, the higher the risk for death by suicide, the researchers found. For example, having a history of seven or more infections was associated with an iRR of 2.90.

The highest risk of suicide was among those with hepatitis and HIV or AIDS.

The researchers observe that their findings are in line with others linking infections, proinflammatory cytokines and inflammatory metabolites to increased risk of suicidal behavior. They also note that the psychological effect of being hospitalized with a severe infection might affect the risk of suicide.

Senior author Dr. Annette Erlangsen of the Danish Research Institute for Suicide Prevention, also in Copenhagen, told Reuters Health by email, "These are intriguing findings and more research is needed to understand the patterns of causality."

The co-author of an accompanying editorial, Dr. Lena C. Brundin of The Van Andel Research Institute in Grand Rapids, Michigan, said, "To find evidence confirming some of the current edge-cutting hypotheses in psychiatric research in an epidemiological study of this scale is highly significant; this is a very impactful study."

"The perspective of utilizing anti-inflammatory and antibiotic medications in psychiatric patients is revolutionary," she told Reuters Health by email. "Importantly, patients prone to suicidal ideation and behavior need to be enrolled in clinical trials rather than being excluded, which is often the case currently."

"The risk for depression and suicides in patients with severe infections should also be carefully considered by clinicians caring for these patients," she concluded. "Psychiatric symptoms are too often neglected in patients that receive hospital care for somatic conditions. The knowledge that inflammation, and infections, can affect the brain and cause severe psychiatric symptoms is very important and should be implemented in general hospital care."

The second study, by Dr. G. David Batty of University College London and colleagues, gives more weight to the role of inflammation.

Using data on more than 39,000 people living in private households in the U.K., the researchers found 26 deaths attributed to suicide over a follow-up of 8.6 years.

A number of factors were significantly associated with an increased hazard of suicide, including being male (hazard ratio, 2.64), being psychologically distressed (HR, 4.89) and being in the highest inflammation group based on serum C-reactive protein (CRP) levels (HR, 4.20).

The positive association between CRP and suicide rates was apparent across the full duration of follow-up, although "the magnitude of this association was somewhat stronger in the early phase," according to the researchers.

"Despite a large sample size, the number of completed suicides herein was modest, leading to low statistical power," they caution. However, the team concludes, other studies are warranted including "large-scale pharmacological trials of inflammation reduction."

SOURCE: http://bit.ly/2aRMsVM, http://bit.ly/2bnROo6 and http://bit.ly/2b9twAw

JAMA Psychiatry 2016.