How does the placebo effect work?

The answer

The placebo effect is a measurable physiological response triggered by the expectation of treatment rather than the treatment itself. When a patient believes they are receiving effective medication, the brain releases endogenous opioids (the body's natural painkillers), dopamine, and other neurochemicals that produce genuine symptom relief. Brain imaging studies show that placebo painkillers activate the same brain regions (periaqueductal gray, nucleus accumbens) as real analgesic drugs. The effect is so powerful that placebo surgery for knee osteoarthritis produced outcomes equal to real surgery in some clinical trials. Remarkably, placebos can work even when patients know they are taking them (open-label placebos), suggesting that the ritual of treatment itself triggers healing responses.