Stress is an inevitable part of life that can profoundly impact social and emotional functioning, contributing to the development of psychiatric disease. One key component of emotion and social processing is facial expressions, which humans can readily detect and react to even without conscious awareness. Facial expressions have been the focus of philosophic and scientific interest for centuries. Historically, facial expressions have been relegated to peripheral indices of fixed emotion states. More recently, affective neuroscience has undergone a conceptual revolution, resulting in novel interpretations of these muscle movements. Here, we review the role of facial expressions according to the leading affective neuroscience theories, including constructed emotion and social-motivation accounts. We specifically highlight recent data (Mayo et al, 2018) demonstrating the way in which stress shapes facial expressions and how this is influenced by individual factors. In particular, we focus on the consequence of genetic variation within the endocannabinoid system, a neuromodulatory system implicated in stress and emotion, and its impact on stress-induced facial muscle activity. In a re-analysis of this dataset, we highlight how gender may also influence these processes, conceptualized as variation in the “fight-or-flight” or “tend-and-befriend” behavioral responses to stress. We speculate on how these interpretations may contribute to a broader understanding of facial expressions, discuss the potential use of facial expressions as a trans-diagnostic marker of psychiatric disease, and suggest future work necessary to resolve outstanding questions.

压力是生活中不可避免的一部分，可以深刻影响社会和情感功能，导致精神疾病的发展。情绪和社会处理的一个关键组成部分是面部表情，即使在没有意识的情况下，人类也可以很容易地察觉到面部表情并做出反应。几个世纪以来，面部表情一直是哲学和科学兴趣的焦点。从历史上看，面部表情一直被归为固定情绪状态的外围指标。最近，情感神经科学经历了一场概念革命，产生了对这些肌肉运动的新颖解释。在这里，我们根据领先的情感神经科学理论回顾面部表情的作用，包括构建的情感和社会动机帐户。我们特别强调最近的数据（Mayo et al, 2018），这些数据展示了压力塑造面部表情的方式以及它如何受到个人因素的影响。我们特别关注内源性大麻素系统（一种与压力和情绪有关的神经调节系统）内遗传变异的后果，及其对压力引起的面部肌肉活动的影响。在对该数据集的重新分析中，我们强调了性别如何影响这些过程，将其概念化为对压力的“战斗或逃跑”或“照顾并成为朋友”行为反应的变化。我们推测这些解释如何有助于更广泛地理解面部表情，讨论面部表情作为精神疾病跨诊断标志的潜在用途，并建议未来解决悬而未决的问题所必需的工作。