Peripheral biological factors and biomarkers of suicide

Discussion on the biological factors and pathophysiological mechanisms of suicidal behavior cannot be limited by the analysis of the processes only in the central nervous system. Number of data testifies that many peripheral systems and processes are involved in the pathological chains, including peripheral serotonin, tryptophan, neurokynurenines, norepinephrine, lipid metabolism, immune system in general and cytokines in particular, neurohormonal reactions and gut microbiota as a component of the “gut-brain” axis. All these systems, as well as their genetic markers, in this or other way appear to be associated with suicidal behavior. Cause-effect relationships in most cases are rather difficult to delineate, it is very probable that all relations are double-ended and network-oriented. Stress reaction, which involves all systems of the organism and triggers physiological processes, behavior, emotions and cognition, is most likely to be an integrating mechanism. All this is important both for understanding of the pathophysiology of suicidality and for the search of peripheral biomarkers of suicidal behavior, which could be useful for better risk prediction and even suicide prevention. Biggest perspectives are on the way of combining different markers, one of the most promising is the functional convergent genomics approach, which gives an example of such combination.