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.

Mounting evidence shows the immune system as important in the pathophysiology of suicidality. The potential triggers of suicidal behavior 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 ultimately lead to suicide in vulnerable individuals. Many more studies are needed.  

For more information, see complete article:

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