Candidate biomarkers of suicide crisis syndrome: what to test next? A concept paper.
There has been increasing interest in both suicide-specific diagnoses within the psychiatric nomenclature and related biomarkers. Because the Suicide Crisis Syndrome (SCS)--an emotional crescendo of several interrelated symptoms--seems to be promising for the identification of individuals at risk of suicide, the aim of the present paper is to review the putative biological underpinnings of the SCS symptoms (entrapment, affective disturbance, loss of cognitive control, hyperarousal, social withdrawal). A PubMed literature search was performed to identify studies reporting a link between each of the 5 SCS symptoms and biomarkers previously reported to be associated with suicidal outcomes. Disturbances in the hypothalamic-pituitary-adrenal axis, with dysregulated corticotropin-releasing hormone and cortisol levels, may be linked to a sense of entrapment. Affective disturbance is likely mediated by alterations in dopaminergic circuits involved in reward and anti-reward systems, as well as endogenous opioids. Loss of cognitive control is linked to altered neurocognitive function in the areas of executive function, attention, and decision-making. Hyperarousal is linked to autonomic dysregulation, which may be characterized by a reduction in both heart rate variability and electrodermal activity. Social withdrawal has been associated with oxytocin availability. There is also evidence that inflammatory processes may contribute to individual SCS symptoms. The SCS is a complex syndrome that is likely the consequence of distinct changes in interconnected neural, neuroendocrine and autonomic systems. Available clinical and research data allow for development of empirically testable hypotheses and experimental paradigms to scrutinize the biological substrates of the SCS.