https://www.health.harvard.edu/mental-health/the-power-of-the-placebo-effect

A study led by Kaptchuk and published in Science Translational Medicine explored this by testing how people reacted to migraine pain medication. One group took a migraine drug labeled with the drug’s name, another took a placebo labeled “placebo,” and a third group took nothing. The researchers discovered that the placebo was 50% as effective as the real drug to reduce pain after a migraine attack.

The researchers speculated that a driving force beyond this reaction was the simple act of taking a pill. “People associate the ritual of taking medicine as a positive healing effect,” says Kaptchuk. “Even if they know it’s not medicine, the action itself can stimulate the brain into thinking the body is being healed.”