Suicide Attempts and Immune Response

Suicide kills more than 40,000 people in the United States every year, an estimated 90% of them with a diagnosable severe psychiatric disease. Yet little is known about what causes some individuals to take their own lives, limiting the ability to reduce the number of such deaths.
Findings from a new study published in the Journal of Psychiatric Research suggest that identifying blood-based antibodies may offer a route to more personalized assessment and treatment of suicide risk and, ultimately, to more effective suicide-attempt prevention. The study compared antibody levels to viruses known to attack and inflame the nervous system in psychiatric patients with a history of suicide attempt and patients who had not attempted suicide.
Findings
In the study by Faith Dickerson and colleagues, 162 patients with schizophrenia, bipolar disorder or major depression were assessed for suicide-attempt history and antibodies to neurotropic infectious agents including Toxoplasma gondii (T. gondii). All the patients were in psychiatric treatment and receiving medication during the study.
Among the participants, statistically significant correlations were found for:

  • Lifetime history of suicide attempt and the level of antibodies to T. gondii
  • Lifetime history of suicide attempt and the level of antibodies to a common herpes virus (cytomegalovirus or “CMV”)
  • Lifetime history of suicide attempt and current cigarette smoking.

Individuals with antibodies to both T. gondii and CMV were found to be at heightened risk of attempting suicide, suggesting that exposure to both viruses might be additive, according to the authors. Individuals with antibodies to both viruses were also more likely to have made multiple suicide attempts.
No statistical correlations were found for:

  • The deadliness of suicide attempt and the level of antibodies to either virus
  • Patient age at time of assessment, gender, race, diagnostic group, clinical care setting, cognitive score, psychiatric symptom score, or any of the medication variables

Implications
Suicide rates in the United States have been rising since the mid-2000s, with more individuals per 100,000 population killing themselves than previously. The 21stCentury Cures Act and other federal, state and local initiatives, as well as many national nonprofits, have focused on reducing suicide risk, but the task remains challenging without clarity about the underlying causes.
While “the mechanisms by which inflammation may be associated with increased suicide risk are not known with certainty,” the authors of this study wrote, “the successful identification of blood-based antibody markets would represent an advance in the prediction and prevention of suicide attempts” among psychiatric patients.
“Suicide, for which a previous suicide attempt is the greatest risk factor, is a major cause of death worldwide and is highly prevalent in patients with serious mental illness,” they conclude. “Unfortunately, the ability to predict suicide remains limited and no reliable biological markers are available. The identification of blood-based antibody markers should provide for more personalized methods for the assessment and treatment, and ultimately prevention, of suicide attempts in individuals with serious mental illnesses.”

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