Suicide is the second leading cause of death worldwide, especially among young adults and adolescents. It is estimated that suicide accounts for 800,000 deaths around the world, according to an editorial
written by Lena C. Brundin, MD, PhD, and Jamie Grit, B.Sc. of the Van Andel Research Institute, and this staggering number might not even be accurate due to the fact that, in many cases, suicide-related deaths are somewhat of a social taboo, and are not as frequently reported. Although the psychological aspects related to suicide have been, and continue to be thoroughly explored, researchers have yet to really examine the biological aspects that could lead to suicide, such as an infection that triggers a potentially harmful inflammatory response.
In their study
, a team of researchers led by Helene Lund-Sorensen, BM, of Copenhagen University Hospital, Denmark, took a closer look at Danish nationwide registers, consisting of over 7.2 million individuals, all above the age of 15 years and living in Denmark between 1980 and 2011. Through these registries, researchers hoped to acquire a better understanding of the link between patients who had been diagnosed with infectious diseases and their level of risk when it comes to suicide-related death.
Of this study population, those individuals who had one or more infection diagnoses since 1977 were noted to have a “history of infection,” according to a news release
from The JAMA Nework
. The aforementioned infections were grouped into specific categories such as pathogen, consisting of bacterial, viral, or “others,” and infection type, which consists of hepatitis, HIV, sepsis, genital, and central nervous system, among others.
A total of 809,384 (11.2%) of the individuals included in the registers were hospitalized with an infection during follow-up. In addition, 32,683 suicides occurred during follow-up, and 7,892 (24.1%) of those individuals who had committed suicide had a previously been infected during hospitalization.
Dr. Lund-Sorensen and her team hypothesized that the infection worked as a kind of “trigger” that caused inflammation, and ultimately, suicidality, according to an editorial on the study by Drs. Brundin and Grit. They also referred to previous “hallmark” studies that showed 30 to 45% of patients who were receiving cytokine-based immunotherapy also had inflammation that triggered depressive symptoms and increased their risk of suicide. The authors also mentioned additional evidence that supports that link of inflammation with increased suicide risk; in depressed as well as suicidal individuals, increased inflammation is present in the brains, the cerebrospinal fluid, as well as in the individuals’ blood. “Elevated levels of interleukin 6 (IL-6) and the inflammatory metabolic quinolinic acid have been found in the cerebrospinal fluid of persons recently attempting suicide,” according to the editorial.