Wolters Fabian, Peerdeman Kaya J, Evers Andrea W M
Health, Medical and Neuropsychology Unit, Institute of Psychology, Faculty of Social and Behavioral Sciences, Leiden University, Leiden, Netherlands.
Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands.
Front Psychiatry. 2019 Jul 2;10:470. doi: 10.3389/fpsyt.2019.00470. eCollection 2019.
Placebo and nocebo effects are, respectively, the helpful and harmful treatment effects that do not arise from active treatment components. These effects have thus far been researched most often in pain. It is not yet clear to what extent these findings from pain can be generalized to other somatic symptoms. This review investigates placebo and nocebo effects in four other highly prevalent symptoms: dyspnea, fatigue, nausea, and itch. The role of learning mechanisms (verbal suggestions, conditioning) in placebo and nocebo effects on various outcomes (self-reported, behavioral, and physiological) of these different somatic symptoms is explored. A search of experimental studies indicated that, as in pain, the combination of verbal suggestion and conditioning is generally more effective than suggestion alone for evoking placebo and nocebo effects. However, conditioning appears more and verbal suggestions less relevant in symptoms other than pain, with the exception of placebo effects on fatigue and nocebo effects on itch. Physiological measures, such as heart rate, lung function, or gastric activity, are rarely affected even when self-reported symptoms are. Neurobiological correlates are rarely investigated, and few commonalities appear across symptoms. Expectations generally predict placebo and nocebo effects for dyspnea and itch but seem less involved in fatigue and nausea. Individual characteristics do not consistently predict placebo or nocebo effects across symptoms or studies. In sum, many conclusions deriving from placebo and nocebo pain studies do appear to apply to other somatic symptoms, but a number of important differences exist. Understanding what type of learning mechanisms for which symptom are most likely to trigger placebo and nocebo effects is crucial for generalizing knowledge for research and therapies across symptoms and can help clinicians to optimize placebo effects in practice.
安慰剂效应和反安慰剂效应分别是并非由积极治疗成分产生的有益和有害治疗效果。迄今为止，这些效应在疼痛研究中最为常见。目前尚不清楚疼痛研究中的这些发现能在多大程度上推广到其他躯体症状。本综述调查了其他四种高度常见症状中的安慰剂效应和反安慰剂效应：呼吸困难、疲劳、恶心和瘙痒。探讨了学习机制（言语暗示、条件作用）在安慰剂和反安慰剂效应中对这些不同躯体症状的各种结果（自我报告、行为和生理）所起的作用。对实验研究的检索表明，与疼痛研究一样，言语暗示和条件作用相结合通常比单独的暗示更有效地诱发安慰剂效应和反安慰剂效应。然而，除了安慰剂对疲劳的效应和反安慰剂对瘙痒的效应外，在疼痛以外的症状中，条件作用似乎更相关，而言语暗示的相关性较小。即使自我报告的症状受到影响，心率、肺功能或胃活动等生理指标也很少受到影响。神经生物学相关性很少被研究，不同症状之间几乎没有共性。期望通常能预测呼吸困难和瘙痒的安慰剂效应和反安慰剂效应，但在疲劳和恶心中似乎作用较小。个体特征并不能始终如一地预测不同症状或研究中的安慰剂效应或反安慰剂效应。总之，许多源自安慰剂和反安慰剂疼痛研究的结论似乎确实适用于其他躯体症状，但也存在一些重要差异。了解哪种症状的学习机制最有可能触发安慰剂效应和反安慰剂效应，对于跨症状的研究和治疗知识的推广至关重要，并且可以帮助临床医生在实践中优化安慰剂效应。
