How do we predict those at risk for suicide? A published analysis supports the notion that levels of cytokines — which are known to promote inflammation — are increased in the bodies and brains of people who are contemplating or have attempted suicide. This is true even when compared to people with the same psychiatric disorders who are not suicidal.

Cytokine levels, the researchers say, may help distinguish patients who are suicidal from patients who are not.

“Immune system dysfunction, including inflammation, may be involved in the pathophysiology of major psychiatric disorders,” Dr. Brian Miller of Georgia Regents University stated in a press release.

Cytokines are chemical messengers, essentially. Within the immune system, cells communicate with one another by releasing and responding to cytokines. A category of small proteins, cytokines include an assortment of interleukins, interferons, and growth factors that help coordinate immune responses.

Inflammation, which is a malfunction of the immune system involving, in part, cytokines, affects every organ and system in the body. High levels of cytokines contribute to arthritis, atherosclerosis, and asthma. Many studies suggest these immune system messengers are released under conditions of psychological stress and resulting inflammation in the brain may contribute to depression.

Miller and his co-researcher, Dr. Carmen Black collected and pooled data from 18 published studies. Altogether, then, they examined information on 583 psychiatric patients who contemplated suicidal, 315 psychiatric patients who were non-suicidal, and 845 healthy control participants. Calculating the numbers, they found suicidal patients had significantly increased levels of two cytokines, interleukin (IL)-1β and IL-6, both in their blood and postmortem brain.

By identifying biological markers generally associated with suicide, the researchers believe, someday a simple blood test may be developed to help doctors predict long-term risk for self-destruction, just as today, high blood pressure helps to forecast physical problems years down the road.

“Given that suicide is a major area of public health concern, it is critical to investigate potential markers of suicidality that could be used to… advance suicide prevention efforts," said Miller.

He and Black say it is necessary to conduct studies of large and diverse patient samples in order to confirm the presence of alterations in cytokine in people who are suicidal. Plus, scientists must evaluate whether controlling inflammation early in life will have a long-term protective effect.

Source: Black C, Miller BJ. Meta-analysis of Cytokines and Chemokines in Suicidality: Distinguishing Suicidal Versus Nonsuicidal Patients. Biological Psychiatry. 2015.