The placebo effect is often described as 'mind over matter', but the phrase understates how physical the phenomenon is. When patients believe they have received a painkiller, their brains release endorphins — the body's own opioids — producing measurable pain relief through the same chemical pathways a real drug would use. This is why modern drug trials must compare a new medicine not against no treatment, but against a placebo: the question is never whether a drug works better than nothing, which is a low bar, but whether it works better than the belief that one is being treated.