Grillon C, Morgan C A, Davis M, Southwick S M
Connecticut VA Medical Center, New Haven, USA.
Am J Psychiatry. 1998 Jun;155(6):812-7. doi: 10.1176/ajp.155.6.812.
Exaggerated startle is a symptom of posttraumatic stress disorder (PTSD), but empirical studies have not consistently documented elevated baseline startle in PTSD. The authors proposed in a previous study that Vietnam veterans with PTSD exhibit exaggerated startle only under stressful conditions. They reported that darkness facilitated startle in humans, suggesting that the startle reflex is sensitive to the aversive nature of darkness. In the present study they tested the hypothesis that the magnitude of facilitation of startle by darkness would be greater in Vietnam veterans with PTSD than in comparison groups of subjects without PTSD. Prepulse inhibition was also investigated.
The magnitude of startle and prepulse inhibition were assessed in alternating periods of darkness and light in 19 nonmedicated Vietnam veterans with PTSD, 13 Vietnam veterans without PTSD, and 20 civilians without PTSD.
The overall startle level was higher in the veterans with PTSD than in either of the two groups of subjects without PTSD. Startle was facilitated by darkness, and the magnitude of this facilitation was greater in the veterans with PTSD than in the civilians without PTSD, but it was not greater in the veterans without PTSD. Prepulse inhibition was not affected by darkness and did not significantly differ among groups.
Contrary to the hypothesis, elevated sensitivity to darkness was specific to individuals with combat experience, not to individuals with PTSD, perhaps because veterans had become aversively conditioned to darkness during their combat experiences. The more general increase in startle reactivity in the veterans with PTSD is consistent with clinical observations and descriptions of symptoms in DSM-IV.
夸张惊吓反应是创伤后应激障碍（PTSD）的一种症状，但实证研究并未始终证明PTSD患者的基线惊吓反应升高。作者在先前的一项研究中提出，患有PTSD的越南退伍军人仅在压力条件下表现出夸张惊吓反应。他们报告称，黑暗会促进人类的惊吓反应，这表明惊吓反射对黑暗的厌恶性质敏感。在本研究中，他们检验了这样一个假设：与无PTSD的对照组相比，黑暗对患有PTSD的越南退伍军人惊吓反应的促进程度更大。同时也对前脉冲抑制进行了研究。
对19名未服药的患有PTSD的越南退伍军人、13名无PTSD的越南退伍军人和20名无PTSD的平民，在黑暗和明亮交替的时间段内评估惊吓反应的程度和前脉冲抑制情况。
患有PTSD的退伍军人的总体惊吓水平高于两组无PTSD的受试者中的任何一组。黑暗促进了惊吓反应，且这种促进程度在患有PTSD的退伍军人中比在无PTSD的平民中更大，但在无PTSD的退伍军人中并非如此。前脉冲抑制不受黑暗影响，且在各组之间无显著差异。
与假设相反，对黑暗的敏感性升高是有战斗经历的个体所特有的，而非PTSD患者所特有，这可能是因为退伍军人在战斗经历中对黑暗产生了厌恶条件作用。患有PTSD的退伍军人惊吓反应性的更普遍增加与临床观察以及《精神疾病诊断与统计手册》第四版（DSM-IV）中的症状描述一致。
