University of California San Diego, La Jolla, California, United States of America.
PLoS One. 2013 Nov 28;8(11):e80507. doi: 10.1371/journal.pone.0080507. eCollection 2013.
Recent evidence suggests that sensitivity to the emotional sequela of experimental thermal pain(measured by emotional unpleasantness) is heightened in individuals with major depressive disorder(MDD), a phenomenon we termed "emotional allodynia". The aim of this study was to examine whether acute happy and sad mood induction alters emotional allodynia in MDD. We hypothesized that emotional allodynia will be a robust characteristic of individuals with MDD compared to healthy controls. Thus, it would remain following acute mood induction, independent of valence.
Twenty-one subjects with current MDD and 21 well-matched healthy subjects(HC) received graded brief temperature stimuli following happy and sad mood inductions procedures(MIP). All subjects rated the intensity and affect(pleasantness/unpleasantness) of each stimulus. Sensory(pain intensity) and affective(pain unpleasantness) thresholds were determined by methods of constant stimuli.
The MIPs reliably induced happy and sad mood and the resulting induced mood and subjective arousal were not different between the groups at the time of temperature stimulation. Compared to HC, MDD individuals demonstrated emotional allodynia. We found significantly decreased affective pain thresholds whereby significantly lower temperatures became unpleasant in the MDD compared to the HC group. This was not observed for the sensory pain thresholds. Within the MDD, the affective pain thresholds were significantly lower than the corresponding pain intensity thresholds, whereby non-painful temperatures were already unpleasant for the MDD irrespective of the induced mood. This was not observed for the HC groups where the affective and pain intensity thresholds were comparable.
These findings suggest that emotional allodynia may be a chronic characteristic of current MDD. Future studies should determine if emotional allodynia persists after psychological or pharmacological interventions. Finally, longitudinal work should examine whether emotional allodynia is a result of or vulnerability for depression and the role it plays in the increased susceptibility for pain complaints in this disorder.
最近的证据表明，在患有重度抑郁症（MDD）的个体中，对实验性热痛的情绪后果（通过情绪不愉快来衡量）的敏感性增强，我们称之为“情绪痛觉过敏”。本研究的目的是检验急性快乐和悲伤情绪诱导是否会改变 MDD 中的情绪痛觉过敏。我们假设与健康对照组相比，MDD 个体的情绪痛觉过敏将是一个显著的特征。因此，它将在情绪诱导后仍然存在，而与情绪效价无关。
21 名当前患有 MDD 的受试者和 21 名匹配良好的健康对照者（HC）在接受快乐和悲伤情绪诱导程序（MIP）后接受了分级短暂温度刺激。所有受试者都对每个刺激的强度和感觉（愉快/不愉快）进行了评分。通过恒定刺激法确定感觉（疼痛强度）和情感（疼痛不愉快）阈值。
MIP 可靠地诱导了快乐和悲伤的情绪，并且在温度刺激时，两组之间的诱导情绪和主观唤醒没有差异。与 HC 相比，MDD 个体表现出情绪痛觉过敏。我们发现情感疼痛阈值显著降低，这意味着 MDD 个体比 HC 个体在较低的温度下会感到不愉快。这在感觉疼痛阈值中没有观察到。在 MDD 中，情感疼痛阈值明显低于相应的疼痛强度阈值，这意味着 MDD 个体在不感到疼痛的温度下已经感到不愉快，而与诱导情绪无关。在 HC 群体中没有观察到这种情况，因为情感和疼痛强度阈值是可比的。
这些发现表明情绪痛觉过敏可能是当前 MDD 的一个慢性特征。未来的研究应该确定情绪痛觉过敏是否在心理或药物干预后仍然存在。最后，纵向研究应该检验情绪痛觉过敏是否是抑郁的结果或易感性，以及它在这种疾病中增加对疼痛抱怨的易感性中所起的作用。
