Placebo can still work even when the patient knows it is a placebo

The classic placebo effect assumes the patient has to believe they're taking a real drug. But in "open-label placebo" experiments, participants are told upfront the pill is empty — and a portion of them still report real improvement, for example in chronic pain or irritable bowel syndrome.

This most likely happens because of the ritual of treatment itself — regularly taking a pill, paying attention to symptoms, expecting improvement — rather than any chemical substance. The brain responds to the context of being treated, not just to what's actually in the pill.

The effect is reproducible across studies, but there's still no single, coherent neurobiological explanation for why knowing "it's just a placebo" doesn't cancel it out — one of medical psychology's more uncomfortable puzzles.

The effect isn't universal or limitless — it doesn't replace treatment for serious illness — but the mere fact that it works despite full transparency undercuts any simple idea of what a "medicine" even is.