1. Suicide can be described by a stress-diathesis model which suggests that the act of suicide is brought about by environmentally based stressors coupled with an underlying tendency toward suicidal behavior.
2. Genomic, neuroimaging, and post-mortem studies implicate altered function of the serotonin neurotransmitter and hypothalamic-pituitary-adrenal axis systems.
3. Biologic differences in these systems present as impaired control of mood, pessimism, impaired problem solving, over-reactivity to negative social signs, and suicidal ideation.
Evidence Rating Level: 3 (Average)
Study Rundown: Suicide is a complex behavior with many complicated facets ranging from stressful life events to biologically altered cognitive process. The identification of suicidal tendency and prevention are important goals in the realm of psychiatric medicine. The stress-diathesis model theorizes that state-dependent stressors such as major life events and a susceptibility to suicidal behavior may combine and lead to suicide. Current research shows that the diathesis or trait-like portion of the model functions independently from psychiatric illness but has specific biological underpinnings of its own. Suicide is linked with a greater number of serotonin neurons and increased tryptophan hydroxylase 2. There also appears to be fewer noradrenergic neurons in the locus coeruleus of individuals who have died of suicide. Beyond the cellular level there are structural differences in the brains of individuals who attempt suicide as well as decreased right-sided basal ganglia and grey matter cortical volumes. It is posited that these biological changes lead to the altered cognitive processes of mood regulation, decision making, and prediction of reward and punishment found in individuals with suicidal behavior.
Early-life adversity or trauma is considered to be a strong risk factor for suicide. Epigenetic mechanisms combine with consequent modification to the hypothalamic-pituitary-adrenal axis are considered as a possible basis for this observation. It is believed that ~50% of the risk for suicide is heritable; however, the exact genes leading to this risk are still largely under contention. Treatment and prevention of suicide must be approached with respect to the stress-diathesis model; managing both the acute nature of suicide as a symptom of psychiatric illness and the longstanding trait-like character of the disease are imperative for positive outcomes.
Strengths of this study include the wide breadth of literature under review and the synthesis of this data to provide a clear view of the topic of suicide. That being said, the literature reviewed is itself composed mainly of review articles and there is no novel data or firm conclusions brought about by the authors.
Relevant Reading: Chapter 6: Stress–diathesis model of suicidal behavior
In-Depth [systematic review]: This study reviews the current literature on suicide and the biological facets that have been elucidated to date. The authors focused on articles within the last 5 years focusing on the search terms “suicide” and “neurobiology”, “genetics”, and “neuroimaging”. Review articles were mainly cited in the reference section given space considerations. As this is a literature review, there are no novel data to be reported. Please refer to the Study Rundown section for important conclusions and findings.
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