网范文：“Neuroeconomics of suicide”自杀行为是当前世界受伤和死亡的主因。有关自杀与抑郁症和精神分裂症等精神疾病,是由于经济的不确定性、社会/文化因素造成。这篇心理范文探讨提出了一种神经方面引起的自杀，对自杀行为进行预测。神经生物学如羟色胺,多巴胺,皮质醇(HPA轴等在脑区，英语论文范文，如眼窝前额，额叶皮层和边缘地区，可能被认为与神经因素导致自杀有关。
当前的框架将基础分子神经经济学为基础，英语论文范文，来探讨自杀行为的决策过程。根据全球每年每100000人接近15个人自杀估计,每年大约有一百万人自杀。自杀行为构成一个主要公共问题。下面的范文进行详述。
Summary
Suicidal behavior is a leading cause of injury and death worldwide. Suicide has been associated with psychiatric illnesses such as depression and schizophrenia, as well as economic uncertainty, and social/cultural factors. This study proposes a neuroeconomic framework of suicide. Neuroeconomic parameters (e.g., risk-attitude, probability weighting, time discounting in intertemporal choice, and loss aversion) are predicted to be related to suicidal behavior. Neurobiological and neuroendocrinological substrates such as serotonin, dopamine, cortisol (HPA axis), nitric oxide, serum cholesterol, epinephrine, norepinephrine, gonadal hormones (e.g., estradiol and progesterone), dehydroepiandrosterone (DHEA) in brain regions such as the orbitofrontal/dorsolateral prefrontal cortex and limbic regions (e.g., the amygdala) may supposedly be related to the neuroeconomic parameters modulating the risk of suicide. The present framework puts foundations for ―molecular neuroeconomics‖ of decision-making processes underlying suicidal behavior.
Keywords: Suicide, Neuroeconomics, risk, intertemporal choice, discounting
Introduction
As the global annual rate of suicide approximates 15 per 100,000 individuals, it is estimated that one million people worldwide commit suicide each year. Annual rates of non-fatal suicidal behaviour are 10–20 times higher than those of completed suicide (Kerkhof, 2017). Suicidal behavior thus constitutes a major public health problem. This indicates the necessity of effective theoretical frameworks for suicide prevention. During the past 30 years, economists have contributed insights about the economic motivations underlying suicidal behavior. Hamermesh and Soss (1974) formalized a model of the utility maximization decision faced by those contemplating suicide. Their , and subsequent work by economists, developed the notion that suicide occurs when the temporally-discounted stream of expected utility (subjective well-being) over a person’s lifetime is sufficiently low, perhaps negative, by assuming the subject’s decision-making is rational.
However, recent studies in behavioral economics and neuroeconomics revealed that people are irrational in terms of economic theory. Therefore, introducing neuroeconomic frameworks is important for a better understanding of suicidal behavior. Also, recent neurobiological studies on suicidal behavior demonstrated that several neurobiological substrates such as serotonin, dopamine, and neuroactive steroid hormones in the brain regions such as the prefrontal cortex and the limbic structures are important determinants of suicidal behavior. Therefore, combining neuroeconomic theory with these neurobiological finding is necessary to establish molecular neurobiological theory of suicidal behavior (―molecular neuroeconomics‖ of suicide). This is organized in the following manner. In Section 2, I briefly introduce neuroeconomic theory of decision under risk and over time, and economic theory of suicidal behavior. In Section 3, findings in neurobiology regarding the molecular mechanisms of suicidal behavior are briefly reviewed. In Section 4, I proposed several predictions from molecular neuroeconomic theory of suicidal behavior. Some conclusions from this study and future study directions by utilizing the present molecular neuroeconomic theory, and how to test the present theory experimentally in future neuroeconomic studies are also discussed.
Decision under risk
In behavioral economics, decision under risk is formulated with Kahneman-Tversky’s prospect theory (Kahneman and Tversky, 1979). In prospect theory, a subjective value of an uncertain outcome x which is received at the probability of p is v(x) w( p), where v(x) is a value function and w( p) is a probability weighting function. The prospect theory’s value function is assumed to be concave for gains, convex for losses, and steeper for losses than for gains.
Brain regions related to suicidal behavior
Suicide has been associated with psychiatric illnesses such as depression and schizophrenia. Regarding neuroanatomy, abnormalities in white matter and limbic gray matter appear to be associated with the occurrence of suicide attempts (van Heeringen et al., 2017). The orbitofrontal cortex, the cingulate cortex and the inferior parietal lobule may be involved in response inhibition, disadvantageous decision-making in a gambling task, and suicide attempts (Jollant et al., 2017; van Heeringen et al., 2017). Serotonergic functioning in the dorsolateral prefrontal cortex correlates significantly with levels of hopelessness, a strong clinical predictor of suicidal behaviour (van Heeringen et al., 2017). The right amygdala hypertrophy may be a risk factor for suicide attempts (Spoletini et al., 2017). The left anterior limb of the internal capsule was further associated with suicidal behavior (Jia et al., 2017)
Serotonin and dopamine
The serotonergic system has been the most widely investigated neuromodulatory system in studies of suicide attempters and completers (Yanagi et al., 2017). CSF-5HIAA was correlated with depression and suicidal behavior (Asberg et al., 1976), although tryptophan hydroxylase isoform 2 gene is not related to suicide in Japanese population (Mouri et al., 2017). Our previous study (Takahashi et al., 2017b) ed that depression is associated with steep temporal discounting in the near future, in line with the finding. Also, taking SSRI (selective serotonin reuptake inhibitor) has been associated with suicidal behavior (Dudley et al., 2017).
Furthermore, mesolimbic dopaminergic transmission has been hypothesized to be reduced in depression and suicide (Bowden et al., 1997). Suda et al. (2017) ed dopamine D2 receptor is associated with suicide. Zhong et al., (2017) ed that serotonin and dopamine determine the shape of the value function in Kahneman-Tversky’s prospect theory (equation 1); i.e., risk aversion and loss aversion. Furthermore, both serotonin and dopamine regulate temporal discounting (Takahashi, 2017). Therefore, involvement of serotonergic and dopaminergic systems in suicide should more extensively been studied by employing neuroeconomic frameworks in future studies. Also, nitric oxide is involved in synaptic neurotransmission and associated with suicide (Cui et al., 2017). Iga et al., (2017) demonstrated that BDNF (brain-derived neurotrophic factor) is associated with suicidal behavior. Therefore, the relation between synaptic neurotransmission and suicide should be examined.
Epinephrine and norepinephrine
Adrenaline (epinephrine) is synthesized from tyrosine and phenylalanine in both the adrenal gland and the brain, and is considered both a hormone and a neurotransmitter. Adrenaline is an activator molecule well known to induce several physiological effects (e.g., increased heart rate) and general cognitive enhancement (e.g., increased awareness and attention). Meana et al., (1992) ed an increase in alpha 2-adrenoceptors in the hypothalamus and frontal cortex in suicide victims. Consistent with the , our previous study (Takahashi et al., 2017b; Takahashi et al., 2017) demonstrated that high level of noradrenergic activity is related to slow temporal discounting, which may result in an increase in the rate of deliberate suicide attempts (i.e., ―lethal foresight‖, Dombrovski et al., 2017).
Neuroactive steroid hormones
The hypothalamic–pituitary–adrenal (HPA) axis is the major biological infrastructure of the human stress system with interconnections between the structures by the hormones CRH, ACTH, and cortisol (a type of glucocorticoids). The abnormalities in HPA may be related to suicide (Kunugi et al., 2017). The expression regulation of the hippocampal glucocorticoid receptor, a key component of the HPA axis, is decreased primarily among suicides (McGowan et al., 2017). Supriyanto et al., (2017) ed a genotype of FK506 binding protein 5 is associated with suicidal behavior. Butterfield et al. (2017) ed that patients who had attempted suicide demonstrated significantly higher DHEA levels than those who had not attempted suicide, indicating the involvement of DHEA in suicidal behavior. Regarding gonadal steroids, low estradiol and progesterone levels were observed to associate with suicidal behavior in women (Baca-Garcia et al., 2017). Our previous studies demonstrated that stress hormones modulate temporal discounting behavior (Takahashi, 2017; Takahashi et al., 2017). In males, testosterone is also associated with temporal discounting (Takahashi et al., 2017). Therefore future studies should investigate how these steroid hormones modulate neuroeconomic parameters, resulting in an exaggerated suicide rate. Furthermore, low serum cholesterol is associated with suicidal behavior (Kunugi et al., 1997).
Implications for neuroeconomics and neurobiolgy of suicidal behavior
This study is the first to present a possible unified framework for molecular neuroeconomic theory of suicide. Our theoretical considerations lead us to the following predictions: (a) neurobiological substrates/alterations which increase loss aversion (λ in equation 1) may increase suicide rates, (b) neurobiological substrates/alterations which increase risk aversion (i.e., decrease α< 1 in equation 3 and 4) in intertemporal choice may increase impulsive suicide attempts, (d) neurobiological substrates/alterations which decrease time-discount rate (k parameters in equation 3 and 4) may increase deliberate, non-impulsive suicide attempt (―lethal foresight‖). Moreover, because suicide attempts are associated with disadvantageous decision-making in the gambling task involving loss (Jollant et al., 2017), it can be predicted that (e) neurobiological substrates/alterations which decrease risk aversion in loss may increase the risk of suicidal behavior. Future neuroeconomic studies should investigate whether these predictions (a)-(e) are correct or not, at the molecular and neuronal level, in addition to the neuroanatomical level. Neuropsychopharmacological treatments may especially be useful for the future investigations. Furthermore, some economic theories incorporated social psychological and cultural factors such as self identity and habit (Becker and Murphy, 2017; Akerlof and Kranton, 2017). These factors, which may be important for a better understanding of suicidal behavior (Sakamoto et al., 2017), should be incorporated into neuroeconomic theory of suicide.)
网站原创范文除特殊说明外一切图文作品权归所有；未经官方授权谢绝任何用途转载或刊发于媒体。如发生侵犯作品权现象，保留一切法学追诉权。
更多范文欢迎访问我们主页 当然有需求可以和我们24小时在线客服 20171 关系交流。-X()
|
