A recent study published in the journal Biological Psychiatry indicates the presence of aberrant cytokine levels in patients with suicidality, and identifies a link between pro-inflammatory cytokines, and specifically, interleukin (IL)-1β and IL-6 with suicidal behavior.
Previous research has shown that major depression is associated with an immune response with an increased production of pro-inflammatory cytokines including IL-1 and IL-6.
More recent data indicate that pre-existing individual differences in the sensitivity of the peripheral immune system may predict the vulnerability to social stress, and that an “IL-6 hyper-responsiveness” is an preexisting trait that may associate with a greater risk of stress-related disorder development such as depression.
It is known that certain cytokines (the ‘immune hormones’ or the chemical messengers between immune cells) contribute to the development of autoimmune diseases and arthritis, atherosclerosis, or allergy and asthma. Some of these cytokines have also been associated with major depression.
In the Biological Psychiatry meta-analysis study, based on 18 studies and including 583 patients with suicidality, Carmen Black and Brian Miller of Georgia Regents University demonstrate that suicidal patients had significantly increased levels of the pro-inflammatory cytokines, IL-1β and IL-6, both in their blood and postmortem brain.
Interestingly, cerebrospinal fluid levels of IL-8 were significantly decreased in patients with suicidality, as compared to control subjects.
Further studies are needed to evaluate whether these cytokines or other biomarkers may help distinguish patients at risk of suicide or associated self-destructive behaviors.