Department of Family medicine, College of Human Medicine, Michigan State University, Grand Rapids, Michigan, United States of America.
Department of Psychology, Wayne State University, Detroit, Michigan, United States of America.
PLoS One. 2020 Mar 6;15(3):e0230030. doi: 10.1371/journal.pone.0230030. eCollection 2020.
Psychological war trauma among displaced refugees is an established risk factor for mental health disorders, especially post-traumatic stress disorder (PTSD). Persons with trauma-induced disorders have heightened neuroplastic restructuring of limbic brain circuits (e.g., amygdala and hippocampus), which are critical factors in the pathophysiology of PTSD. Civilians in war are exposed to both psychological trauma and environmental hazards, such as metals. Little is known about the possible mental health impact from such environmental exposures, alone or in combination with trauma. It is of special interest to determine whether war exposures contribute to dysfunctional neuroplasticity; that is, an adverse outcome from sustained stress contributing to mental health disorders. The current study examined Middle Eastern refugees in the United States to determine the relationships among pre-displacement trauma and environmental exposures, brain derived neurotrophic growth factor (BDNF) and nerve growth factor (NGF)-two neurotrophins reported to mediate neuroplasticity responses to stress-related exposures-and mental health.
Middle Eastern refugees (n = 64; 33 men, 31 women) from Syria (n = 40) or Iraq (n = 24) were assessed 1 month after arrival to Michigan, US. Participants were interviewed in Arabic using a semi-structured survey to assess pre-displacement trauma and environmental exposure, PTSD, depression, anxiety, and self-rated mental health. Whole blood was collected, and concentrations of six heavy metals as well as BDNF and NGF levels were determined. Because these two neurotrophins have similar functions in neuroplasticity, we combined them to create a neuroplasticity index. Linear regression tested whether psychosocial trauma, environmental exposures and biomarkers were associated with mental health symptoms.
The neuroplasticity index was associated with PTSD (standardized beta, β = 0.25, p < 0.05), depression (0.26, < 0.05) and anxiety (0.32, < 0.01) after controlling for pre-displacement trauma exposures. In addition, pre-displacement environmental exposure was associated with PTSD (0.28, < 0.05) and anxiety (0.32, < 0.05). Syrian refugees and female gender were associated with higher scores on depression (0.25, < 0.05; 0.30, < 0.05) and anxiety scales (0.35, < 0.01; 0.27, < 0.05), and worse on self-rated mental health (0.32, < 0.05; 0.34, < 0.05). In bivariate analysis, the neuroplasticity index was related to blood lead levels (r = 0.40; p < 0.01).
The current study confirms the adverse effects of war trauma on mental health. Higher levels of biomarkers of neuroplasticity correlated with worse mental health and higher blood lead levels. Higher neurotrophin levels in refugees might indicate dysfunctional neuroplasticity with increased consolidation of adverse war memories in the limbic system. Such a process may contribute to psychiatric symptoms. Further research is needed to clarify the pathobiological mechanisms linking war trauma and environmental exposures to adverse mental health.
流离失所难民的心理创伤是精神健康障碍的一个既定风险因素，尤其是创伤后应激障碍（PTSD）。创伤引起的障碍患者的边缘大脑回路（如杏仁核和海马体）的神经可塑性重构增强，这是 PTSD 病理生理学的关键因素。战争中的平民既受到心理创伤的影响，也受到环境危害的影响，例如金属。对于环境暴露单独或与创伤结合可能对心理健康产生的影响知之甚少。特别感兴趣的是确定战争暴露是否会导致神经可塑性功能障碍；也就是说，持续的压力造成的不良后果会导致精神健康障碍。目前的研究在美国的中东难民中进行，以确定流离失所前的创伤和环境暴露、脑源性神经营养因子（BDNF）和神经生长因子（NGF）之间的关系——这两种神经营养因子据报道可调节与应激相关的暴露的神经可塑性反应——以及心理健康。
来自叙利亚（n = 40）或伊拉克（n = 24）的中东难民（n = 64；33 名男性，31 名女性）在抵达美国密歇根州后 1 个月接受评估。参与者使用阿拉伯语进行半结构化访谈，以评估流离失所前的创伤和环境暴露、创伤后应激障碍、抑郁、焦虑和自我报告的心理健康状况。采集全血，测定六种重金属以及 BDNF 和 NGF 水平。由于这两种神经营养因子在神经可塑性方面具有相似的功能，因此我们将它们结合起来创建了一个神经可塑性指数。线性回归测试了心理社会创伤、环境暴露和生物标志物是否与心理健康症状相关。
在控制流离失所前创伤暴露后，神经可塑性指数与 PTSD（标准化β，β=0.25，p<0.05）、抑郁（0.26，<0.05）和焦虑（0.32，<0.01）相关。此外，流离失所前的环境暴露与 PTSD（0.28，<0.05）和焦虑（0.32，<0.05）相关。叙利亚难民和女性性别与抑郁（0.25，<0.05；0.30，<0.05）和焦虑量表（0.35，<0.01；0.27，<0.05）的评分较高，以及自我报告的心理健康状况较差（0.32，<0.05；0.34，<0.05）相关。在双变量分析中，神经可塑性指数与血铅水平呈正相关（r=0.40；p<0.01）。
目前的研究证实了战争创伤对精神健康的不利影响。更高水平的神经可塑性生物标志物与更差的心理健康和更高的血铅水平相关。难民中更高的神经营养因子水平可能表明神经可塑性功能障碍，边缘系统中与战争相关的不良记忆的巩固增加。这一过程可能会导致精神症状。需要进一步研究来阐明将战争创伤和环境暴露与不良心理健康联系起来的病理生物学机制。
