The evolutionary puzzle of suicide

Understanding the neural basis of survival instinct vs. suicidal behavior: a key to decode the biological enigma of human suicidal behavior

Suicidal behavior is a globally widespread psychiatric disorder with a high rate of mortality. Suicide causes psychological and economic hardships for the families and societies, necessitating the development of effective prevention and treatment programs. However, a clear understanding of the neural basis of suicidal behavior would be essential to develop clinically effective therapies. To date, several neurobiological studies have reported the genetic and epigenetic factors, brain regions, and neurotransmitters involved in suicidal behavior; but, a clear understanding of the origins of self-destructive tendencies is lacking. The high prevalence of self-destructive tendency, a potential hallmark of suicidal behavior presents a biological enigma in light of the evolutionarily pervasive struggle for existence and survival (self-preservation instinct). The potential neural correlates of suicidality and survival behavior have been separately investigated. Several regions of prefrontal cortex were implicated in suicide, while the survival circuits regulating the life-processes (defense, thermoregulation, energy and nutrition, fluid balance, and reproduction) include hypothalamus, amygdala, and parabrachial nucleus, among other structures. Future research to understand the possible influence of malfunctioning survival circuits in suicide could provide valuable insights into suicidal behavior. In addition, understanding the possible evolutionary significance of suicidal traits can help us understand the mechanisms of evolution, and also serve towards alleviation of social stigma around suicide. Thus, future research to unravel the biological correlates of survival vs. suicidal instincts, equipped with high-resolution neuroimaging techniques, would be clinically and socially advantageous towards suicide prevention and treatment.

Choosing Death Over Survival: A Need to Identify Evolutionary Mechanisms Underlying Human Suicide

The act of killing self contradicts the central purpose of human evolution, that is, survival and propagation of one’s genetic material. Yet, it continues to be one of the leading causes of human death. A handful of theories in the realm of evolutionary psychology have attempted to explain human suicide. The current article analyses the major components of certain prominent viewpoints, namely, Inclusive fitness, Bargaining model, Pain-Brain model, Psychological aposematism, and few other perspectives. The article argues that relatively more weightage has been given to understanding ultimate (the “why”) rather than proximate (the “how”) functionality of suicidal acts. Evolutionary theorists have consistently pointed out that to comprehensively understand a trait or behavior, one needs to delineate not only how it supports survival but also the evolution of the mechanisms underlying the trait or behavior. Existing theories on suicide have primarily focused on its fitness benefits on surviving kin instead of providing evolutionary explanations of the more complex mechanisms leading up to such self-destructive motivations. Thus, the current paper attempts to highlight this gap in theorizing while suggesting probable proximate explanations of suicide which stresses the need to diffuse attention paid to fitness consequences of the act alone. We speculate that such explorations are needed in order to build a robust and comprehensive evolutionary theory of human suicide.

Decomposing implicit associations about life and death improves our understanding of suicidal behavior

The Death/Suicide Implicit Association Test (IAT) is effective at detecting and prospectively predicting suicidal thoughts and behaviors. However, traditional IAT scoring procedures used in all prior studies (i.e., D-scores) provide an aggregate score that is inherently relative, obfuscating the separate associations (i.e., "Me = Death/Suicide," "Me = Life") that might be most relevant for understanding suicide-related implicit cognition. Here, we decompose the D-scores and validate a new analytic technique called the Decomposed D-scores ("DD-scores") that creates separate scores for each category ("Me," "Not Me") in the IAT. Across large online volunteer samples (N > 12,000), results consistently showed that a weakened association between "Me = Life" is more strongly predictive of having a history of suicidal attempts than is a stronger association between "Me = Death/Suicide." These findings replicated across three different versions of the IAT and were observed when calculated using both reaction times and error rates. However, among those who previously attempted suicide, a strengthened association between "Me = Death" is more strongly predictive of the recency of a suicide attempt. These results suggest that decomposing traditional IAT D-scores can offer new insights into the mental associations that may underlie clinical phenomena and may help to improve the prediction, and ultimately the prevention, of these clinical outcomes.

Female Gender, Marital and Family Problems, and Feelings of Guilt Are Related to Self-Immolation Suicide Attempts

BACKGROUND

Self-immolation (SI) is considered one of the most painful, dramatic, and at the same time most inexplicable methods of suicide, with a high social impact. Prevalence rates are particularly high in Iran, and in north-western Iran specifically. Here, we report sociodemographic, psychological, and psychiatric characteristics of patients attempting self-immolation (PSIs), compared to patients with accident burns (PABs).

METHOD

Patients referred to the Burns Emergency Unit of the Besat Hospital (Hamadan, Iran) were enrolled in the present study between winter 2015 and summer 2016. After burn-related treatments and surgery, a thorough interview was undertaken covering sociodemographic characteristics, burn-related information, and psychiatric background.

RESULTS

A total of 79 patients were enrolled. Among these, 19 (31.7%) had attempted suicide via SI. Compared to the PABs, the PSIs were predominantly females; they reported family and marital problems as the main triggers for SI. The psychiatric interviews indicated that PSIs often suffered from major depressive disorders, adjustment disorders, and bipolar disorders. The prevailing feelings reported were guilt and shame. A binary logistic regression showed that feelings of guilt and marital and family problems predicted SI.

CONCLUSIONS

The prevalence of SI was surprisingly high. Marital and family conflicts as a proxy for highly distressing social interactions, along with female gender and feelings of guilt and shame were strongly associated with SI. Family and couple counseling specifically tailored to difficulties experienced by women might reduce the risk of SI.

Psychological pathway to suicidal ideation among men who have sex with men in Shanghai, China: A structural equation model

We aimed to explore the relationships and develop an inter-theoretical model among psychological variables in the progression to suicidal ideation among men who have sex with men (MSM). A cross-sectional study was conducted among 547 MSM in four districts in Shanghai from March to May in 2014. Socio-demographic, psychological, and behavioral information of the participants was collected. A structural equation model (SEM)-Path Analysis was constructed to interpret the intricate relationships among various psychological variables. Suicidal ideation among MSM during the past year was 10.6%. The developed model agreed well with existing suicide models and had a good fit to the data (χ²/df = 2.497, comparative fit index = 0.983, root mean squared error of approximation = 0.052). Suicidal ideation was predicted by perceived defeat and entrapment (β = 0.21, p < 0.001), which was in turn predicted by temperament (β = 0.60, p < 0.001) and perceived social support (β = 0.34, p < 0.001). Perceived social support fully mediated the relationships among mood states, perceived social status, and perceived defeat and entrapment. MSM with certain types of temperament might be predisposed to a higher perception of defeat and entrapment. Perceived social support can effectively alleviate the negative appraisals and emotions and lower the risk for suicidal ideation among MSM.

Suicide as a derangement of the self-sacrificial aspect of eusociality

Building upon the idea that humans may be a eusocial species (i.e., rely on multigenerational and cooperative care of young, utilize division of labor for successful survival), we conjecture that suicide among humans represents a derangement of the self-sacrificial aspect of eusociality. In this article, we outline the characteristics of eusociality, particularly the self-sacrificial behavior seen among other eusocial species (e.g., insects, shrimp, mole rats). We then discuss parallels between eusocial self-sacrificial behavior in nonhumans and suicide in humans, particularly with regard to overarousal states, withdrawal phenomena, and perceptions of burdensomeness. In so doing, we make the argument that death by suicide among humans is an exemplar of psychopathology and is due to a derangement of the self-sacrificial behavioral suite found among eusocial species. Implications and future directions for research are also presented.