心理预期是具有方向性的,可分为正性(积极的)和负性(消极的)预期,它们相互对立,并对人的身心状况产生不同的影响。在长久以来的临床实践中,预期对疾病治疗和某些生理体验的强大调节作用逐渐为人们所知,并根据其调节方向的不同催生出两个重要概念,即安慰剂与反安慰剂效应。目前关于安慰剂与反安慰剂的研究主要集中在疼痛领域。出人意料的是,尽管二者在疼痛调节上具有相似的心理机制,其内在神经基础并不完全相同:安慰剂效应与反安慰剂效应分别由阿片肽系统和胆囊收缩素系统所介导;在影像学研究中,疼痛加工系统和脊髓在安慰剂/反安慰剂的调节下呈现相反的激活模式,而海马在反安慰剂中的活动具有特异性。
Expectation can bidirectionally regulate diseases or sensory experiences. In terms of pain field, positive expectation alleviates pain (i.e., placebo effect); while negative expectation makes it worse (i.e., nocebo effect). So far, most of researches on placebo and nocebo effect mainly come from the field of pain. Interestingly, although placebo and nocebo share similar psychological processes in modulating pain, the neurophysiological mechanisms underlying the placebo and nocebo are different. Placebo analgesia might be involved with endogenous opioids system. On the contrary, the nocebo effect is considered to be mediated by cholecystokinin (CCK). In addition, brain imaging researches suggested that placebo and nocebo could lead to contrary activation patterns in pain-related networks. Some areas such as the hippocampus were specifically activated in nocebo condition.