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The placebo effect is one of medicine's strangest puzzles. In carefully run trials, patients given an inactive pill sometimes report genuine relief from pain or nausea, even when no active drug is present. Researchers think expectation plays a central role: believing that help is coming can prompt the brain to release its own pain-dampening chemicals. Remarkably, some benefit persists even when patients are told outright that the pill is inert, a finding that has forced scientists to rethink how much of recovery depends on ritual and belief. Far from being mere imagination, the response is now studied as a measurable biological event.