placebos can produce measurable biochemical changes. The paradigm-altering demonstration of this phenomenon came in a 1978 study, from the University of California, San Francisco, of people recovering from dental surgery. The patients were given IV drips of either morphine or a plain saline solution to block their pain; as expected, some “placebo responders” had reductions in pain even though they only received saline. The researchers then added a drug called naloxone, which counteracts overdoses of morphine and heroin by blocking the body’s opioid receptors. This immediately shut off the
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