Wars have been and remain a constant companion of humans throughout history, and nothing seems to suggest that a time free of wars will soon come to be reality. Multiple studies and observations suggest that combat veterans are at increased risk for attempting and dying by suicide. Suicide among combat veterans is an important issue across the world. In 2014, more than 7,400 U.S. military veterans died by suicide, accounting for 18% of all deaths by suicide in the U.S., notwithstanding the fact that veterans make up only 8.5% of the U.S. population. These greater rates of suicide may be related to the fact that military servicemembers are in danger of death each day and may be desensitized to it. Also, combat veterans are subjected to various chemical, physical, and environmental factors that may alter the brain. A psychobiological condition of combat veterans is dissimilar from a psychobiological state of non-combat veterans and civilians. In many ways that influences their suicide risk; combat veterans are not like the general population. The exceptionality of the experience of military combat as a contributor to suicidal behavior merits specific investigation of neurobiological factors that may be associated with suicidality in combat veterans. In this article, I will discuss our and some other studies and suggest that more research into the neurobiology of suicidal behavior among combat veterans is needed. There are very few studies of the neurobiology of suicidality among combat veterans. We have performed investigations of the neurobiology of suicidal behavior in combat military veterans. We compared combat veterans with or without a history of post-deployment suicide attempts, and found that suicide attempters had higher suicidal ideation scores in comparison to non-attempters. Our studies indicate that combat veterans with a history of attempting suicide remain at elevated suicide risk long after the attempt. In our studies, suicide attempters had significantly lower blood levels of dehydroepiandrosterone (DHEA) and dehydroepiandrosterone sulfate (DHEA-S) compared to non-attempters. Decreased amounts of DHEA and DHEA-S may result in elevated susceptibility to neurotoxic influences of stress and contribute to the neurobiology of stress-related disorders and suicidality. We observed that DHEA-S concentrations correlated negatively with suicidal ideation scores in suicide non-attempters, but not in attempters. Possibly, as psychiatric conditions progress, the level of DHEA-S decreases; hence, the neuroprotection provided by DHEA-S is considerably reduced or lost, leading to increased suicidality. We have also examined a relation between two endogenous opioids, anandamide (AEA) and 2-arachidonoylglycerol (2-AG), with suicidal behavior and suicidality in combat veterans. We were interested in the role of endogenous cannabinoids in the neurobiological mechanisms of suicidality among combat veterans because changes in endocannabinoid signaling may play a role in the development of stress-related psychiatric conditions, including mood disorders and posttraumatic stress disorder (PTSD). Our interest was also related to the fact that veterans often use cannabis, and that an association has been observed between use of cannabis among Iraq/ Afghanistan-era veterans and suicidal behavior. We found that, controlling for gender, 2-AG blood concentrations were greater among suicide attempters compared to non-attempters. We also found that AEA blood concentrations correlated negatively with suicidal ideation scores among suicide attempters, but not among non-attempters. AEA appears to reduce suicidality among suicide attempters, i.e., AEA plays a part in the secondary prevention of suicide attempt. AEA may diminish suicidality because the endocannabinoid system restricts activation of the stress reaction by way of disseminated actions in limbic and hypothalamic circuits in the brain. Our research suggests that clinically detected dissimilarities between combat military veterans with vs. without a history of postdeployment suicide attempts may have a neurobiological origin. Other researchers have also studied the neurobiology of suicide among combat veterans. One research group compared platelet serotonin concentrations in five groups of male individuals: suicidal and non-suicidal combat veterans with combat-related PTSD, suicidal and nonsuicidal psychiatric patients without PTSD, and healthy controls. Platelet serotonin concentrations were significantly lower in suicidal PTSD and non-PTSD patients compared to non-suicidal PTSD and non-PTSD patients

中文翻译：

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退伍军人自杀行为的神经生物学

纵观历史，战争一直是并且仍然是人类的永恒伴侣，而且似乎没有任何迹象表明没有战争的时代会很快成为现实。多项研究和观察表明，退伍军人尝试自杀和死于自杀的风险增加。退伍军人的自杀是全世界的一个重要问题。2014 年，超过 7,400 名美国退伍军人死于自杀，占美国所有自杀死亡人数的 18%，尽管退伍军人仅占美国人口的 8.5%。这些更高的自杀率可能与军人每天都有死亡危险并且可能对此不敏感有关。此外，退伍军人会受到可能改变大脑的各种化学、物理和环境因素的影响。退伍军人的心理生物学状况与非战斗退伍军人和平民的心理生物学状况不同。在许多方面影响他们的自杀风险；退伍军人不像一般人群。军事战斗经验作为自杀行为促成因素的特殊性值得对可能与退伍军人自杀相关的神经生物学因素进行具体调查。在本文中，我将讨论我们的研究和其他一些研究，并建议需要对退伍军人自杀行为的神经生物学进行更多研究。很少有关于退伍军人自杀神经生物学的研究。我们对战斗退伍军人的自杀行为的神经生物学进行了调查。我们比较了有或没有部署后自杀未遂史的退伍军人，发现与未尝试自杀者相比，未遂自杀者的自杀意念得分更高。我们的研究表明，有自杀未遂历史的退伍军人在尝试自杀后很长时间内仍处于较高的自杀风险。在我们的研究中，与未尝试自杀者相比，自杀未遂者的血液中脱氢表雄酮 (DHEA) 和硫酸脱氢表雄酮 (DHEA-S) 水平显着降低。DHEA 和 DHEA-S 的量减少可能会导致对压力的神经毒性影响的易感性增加，并导致压力相关疾病和自杀倾向的神经生物学。我们观察到 DHEA-S 浓度与未尝试自杀者的自杀意念得分呈负相关，但与尝试者无关。可能，随着精神疾病的进展，DHEA-S 的水平会降低；因此，DHEA-S 提供的神经保护作用大大减少或丧失，导致自杀倾向增加。我们还研究了两种内源性阿片类药物 anandamide (AEA) 和 2-花生四烯酸甘油 (2-AG) 与退伍军人的自杀行为和自杀倾向之间的关系。我们对内源性大麻素在退伍军人自杀的神经生物学机制中的作用很感兴趣，因为内源性大麻素信号的变化可能在与压力相关的精神疾病的发展中发挥作用，包括情绪障碍和创伤后应激障碍 (PTSD)。我们的兴趣还与退伍军人经常使用大麻的事实有关，并且已经观察到伊拉克/阿富汗时代退伍军人使用大麻与自杀行为之间存在关联。我们发现，控制性别后，与未尝试自杀者相比，自杀未遂者的 2-AG 血液浓度更高。我们还发现，AEA 血液浓度与自杀未遂者的自杀意念评分呈负相关，但在未尝试者中则没有。AEA 似乎可以降低自杀未遂者的自杀倾向，即 AEA 在自杀未遂的二级预防中发挥作用。AEA 可能会降低自杀倾向，因为内源性大麻素系统通过大脑边缘和下丘脑回路中的传播作用来限制应激反应的激活。我们的研究表明，临床检测到的战斗退伍军人与普通军人之间存在差异。如果没有部署后自杀企图的历史，则可能有神经生物学起源。其他研究人员也研究了退伍军人自杀的神经生物学。一个研究小组比较了五组男性个体的血小板血清素浓度：患有与战斗相关的 PTSD 的自杀和非自杀退伍军人、没有 PTSD 的自杀和非自杀精神病患者，以及健康对照组。与非自杀性 PTSD 和非 PTSD 患者相比，自杀性 PTSD 和非 PTSD 患者的血小板血清素浓度显着降低 有战斗相关 PTSD 的自杀和非自杀退伍军人，没有 PTSD 的自杀和非自杀精神病患者，以及健康对照。与非自杀性 PTSD 和非 PTSD 患者相比，自杀性 PTSD 和非 PTSD 患者的血小板血清素浓度显着降低 有战斗相关 PTSD 的自杀和非自杀退伍军人，没有 PTSD 的自杀和非自杀精神病患者，以及健康对照。与非自杀性 PTSD 和非 PTSD 患者相比，自杀性 PTSD 和非 PTSD 患者的血小板血清素浓度显着降低