Abstract
Consistent evidence indicates the association between inflammatory markers and suicidal behavior. The burden related to immunological differences have been widely documented in both major affective disorders and suicidal behavior. Importantly, abnormally elevated pro-inflammatory cytokines levels have been reported to correlate with suicidal behavior but whether and to what extent specific inflammatory cytokines abnormalities may contribute to our understanding of the complex pathophysiology of suicide is unknown. The present manuscript aimed to systematically review the current literature about the role of pro-inflammatory cytokines in suicidal behavior. Most studies showed a link between abnormally higher interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1, vascular endothelial growth factor (VEGF), kynurenic acid (KYN), and lower IL-2, IL-4, and interferon (IFN)-γ levels in specific brain regions and suicidal behavior. Unfortunately, most studies are not able to exclude the exact contribution of major depressive disorder (MDD) as a mediator/moderator of the link between inflammatory cytokines abnormalities and suicidal behavior. The association between suicidal patients (both suicide attempters or those with suicidal ideation) and the altered immune system was documented by most studies, but this does not reflect the existence of a specific causal link. Additional studies are needed to clarify the immune pathways underlying suicidal behavior.
Highlights
Suicidal behavior, which is frequently linked to mood disorders, in particular major depression, is a fundamental public health concern associated with significant disability and psychosocial impairment worldwide [1,2,3]
Social inclusion, whereas IL-2 was positively associated with activation of the right anterior cingulate cortex (ACC), insula and orbitofrontal cortex (OFC) even after controlling independently for the suicidal status
The GR inducible target gene glucocorticoid-induced leucine zipper (GILZ) messenger ribonucleic acid (mRNA) levels were decreased in PFC and amygdaloidal nuclei of these subjects as well. Based on another recent study [27], tumor necrosis factor (TNF)-α expression was significantly higher in the dorsolateral prefrontal cortex of suicide subjects regardless of psychiatric diagnosis, its expression was enhanced even in major depressive disorder (MDD) subjects who died by causes other than suicide
Summary
Suicidal behavior, which is frequently linked to mood disorders, in particular major depression, is a fundamental public health concern associated with significant disability and psychosocial impairment worldwide [1,2,3]. Major depression may be considered one of the leading causes of suicide worldwide with a more than 20-fold increased risk and at least half of all completed suicides which are linked to depressive disorders [1]. Suicidal behavior associated with major depression occurs predominantly in the elderly due to the emergence of psychotic symptoms [1]. Res. Public Health 2020, 17, 2393; doi:10.3390/ijerph17072393 www.mdpi.com/journal/ijerph
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