Placebo is critical for evaluating medical interventions, but it’s also clear that the biology underpinning the placebo effect in humans could have significant clinical and societal impacts. Placebo effects, real responses to false cues, potentially stand at odds with the view that, for adaptive reasons, organisms respond only to true environmental cues. In placebo effects, phenotypic responses are seen in the absence of a biologically active agent. The reason for the increase in the placebo response is largely unknown, but several attempts have been made to overcome this problem. How placebos work is still not quite understood, but it involves a complex neurobiological reaction that includes everything from increases in feel-good neurotransmitters, like endorphins and dopamine, to greater activity in certain brain regions linked to moods, emotional reactions, and self-awareness. All of it can have therapeutic benefit. Reacting to a placebo is not proof that a certain treatment doesn’t work, but rather that another, non-pharmacological mechanism may be present. If placebo responses seen in humans are the result of phenotypic plasticity, then placebo-like effects should be observable in other species—particularly in cases where the environment has been altered to disrupt its reliability. This is the case, and placebo-like effects are seen in a variety of model systems.

安慰剂对于评估医疗干预至关重要，但同样清楚的是，支撑人体安慰剂效应的生物学可能会产生重大的临床和社会影响。安慰剂效应，即对错误线索的真实反应，可能与以下观点不一致：出于适应性原因，生物体只对真实环境线索作出反应。在安慰剂效应中，在没有生物活性剂的情况下可以看到表型反应。安慰剂反应增加的原因在很大程度上是未知的，但已经进行了几次尝试来克服这个问题。安慰剂是如何起作用的还不是很清楚，但它涉及到一个复杂的神经生物学反应，包括从感觉良好的神经递质（如内啡肽和多巴胺）的增加，到与情绪相关的某些大脑区域的更大活动，情绪反应和自我意识。所有这些都可以产生治疗益处。对安慰剂产生反应并不能证明某种治疗无效，而是可能存在另一种非药理学机制。如果在人类中看到的安慰剂反应是表型可塑性的结果，那么在其他物种中应该可以观察到类似安慰剂的效果——特别是在环境发生改变以破坏其可靠性的情况下。情况就是这样，在各种模型系统中都可以看到类似安慰剂的效果。那么在其他物种中应该可以观察到类似安慰剂的效果——特别是在环境被改变以破坏其可靠性的情况下。情况就是这样，在各种模型系统中都可以看到类似安慰剂的效果。那么在其他物种中应该可以观察到类似安慰剂的效果——特别是在环境被改变以破坏其可靠性的情况下。情况就是这样，在各种模型系统中都可以看到类似安慰剂的效果。