Researchers from the Copenhagen University Hospital of Denmark find that individuals who are hospitalized with infections have an increased risk of suicide ideation and death; individuals infected with hepatitis and HIV or AIDS have the highest risk of suicide-related death.
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.
In addition to using the Danish Cause of Death Register to determine risk of suicide-related death, Dr. Lund-Sorenson and her team used incidence rate ratios and accompanying 95% Cis to measure relative risk, according to the study. The study’s results found that there was a 42% higher risk of suicide-related death in individuals who were hospitalized with an infection compared to those who were not infected. In addition, the researchers noted that two other factors were also linked to an elevated risk for suicide-related death: the number of infections and the length of the treatment. The more infections the individual had, and the longer they were on a treatment plan, the higher their risk was for suicide-related death.
Drs. Brundin and Grit wrote, “Strengthening the case for a possible causal role of infections in the pathogenic process that leads to suicide, these researchers show that an increased risk of suicide was associated with the length of treatment and with an increasing number of hospitalizations with infections. Individuals with seven or more infections had an increased risk of suicide of almost 300 percent.”
Individuals with the highest risk of suicide were those infected with hepatitis or HIV/AIDs, “which is in line with previous findings that these patients report higher levels of suicidal ideation and behavior than the general population,” according to the study, "[and] HIV or AIDS infection is strongly linked with psychiatric disorders (eg, depression and substance use).” Using a sensitivity analysis, the researchers found that compared to individuals who were diagnosed with a psychiatric disorder but did not have an infection, individuals who had been diagnosed with an infection before any kind of psychiatric disorder showed an increased risk of suicide-related death. However, the researchers do admit that the suicidal risk of a hospitalized patient with severe infection could be influenced by psychological factors.
The researchers were not able to determine if depression and other risk factors for suicide-related deaths could be associated with the individual’s self-care, and thus, could be linked to severity of infection. In addition, they noted that another limitation to their study was that they were unable to determine if disability due to severe infection or hospital treatment itself could explain risks for suicide-related deaths, according to the news release.
In their study, the researchers concluded, “Our findings indicate that infections may have a relevant role in the pathophysiological mechanisms of suicidal behavior. Provided that the association between infection and the risk of death by suicide was causal, identification and early treatment of infections could be explored as a public health measure for prevention of suicide. Still, further efforts are need to clarify the exact mechanisms by which infection influences human behavior and risk of suicide.”