What is the placebo effect and how does it work?

When people believe they are receiving effective treatment, their brains can release endorphins, dopamine and other neurochemicals that reduce pain and improve symptoms. Brain imaging studies show that placebos activate the same reward and pain-modulation circuits as real drugs. The effect is stronger when the patient trusts the doctor, when the placebo looks like an expensive or potent drug, and when treatment is given in a clinical setting. Even the colour and size of a pill can matter: red pills tend to work better as stimulants and blue as sedatives. Remarkably, some studies show placebos work even when patients are told they are receiving a placebo (“open-label” placebos).