In looking at the biological factors involved in suicide, inflammation and inflammatory conditions such as traumatic brain injuries, autoimmune disorders, and neuropsychiatric symptoms are only beginning to be explored. The immune system is being looked at as important in the pathophysiology of suicidality. Potential triggers of suicidal behavior can include various inflammatory conditions (TBI, vitamin deficiency, autoimmune disorders, and infections), which, through raised levels of inflammation, can cause cause significant problems for individuals. These neurobiological effects might cause profound changes in emotion and behavior, which could lead to suicidal behavior in vulnerable individuals. Suicide is multi-factorial, and many more studies are needed in this area. 

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https://pubmed.ncbi.nlm.nih.gov/27377015/