How powerful is the placebo effect and can it cause real physical changes?

The answer

The placebo effect produces measurable physiological changes, not just subjective reports. Placebo painkillers trigger genuine endorphin release detectable via PET imaging, reducing pain by 15-30% - an effect blocked by the opioid antagonist naloxone, proving real biochemistry is involved. Placebo surgery for knee osteoarthritis proved equally effective as actual arthroscopic surgery in a landmark 2002 New England Journal of Medicine trial. Parkinson's patients given placebos showed measurable dopamine release in brain scans. Remarkably, Ted Kaptchuk's 2010 Harvard study showed placebos worked even when patients were told they were receiving sugar pills - 'open-label placebos' improved IBS symptoms by 59%. Placebo responses have been strengthening over time; a 2015 meta-analysis found pain placebo effects in US trials increased by 30% between 1990 and 2013.