Quoted from The Hundred Year Lie:

Harvard Medical School professor Jerry Avorn describes in his book Powerful Medicines how a placebo can be just as effective as synthetic drugs, with many fewer side effects. “A pivotal paper published in the British journal The Lancet in 1978 placed the once touchy-feely placebo effect firmly in the realm of hard-science neuropharmacology. The study started out as a typical pain experiment: volunteers were given an inert placebo and, as expected, a substantial proportion of them reported that it reduced their pain. But when these subjects were given the opioid blocker naloxone, it blocked the placebo benefit as well. This suggested that the placebo effect results in part from a person’s capacity to secrete homemade narcotics within the brain itself.” Avorn says the proven benefits of the placebo give “new meaning to the once-dismissive phrase, ‘It’s all in your head.’”

Here is just a sampling of the range of medical evidence emerging for the healing powers of placebos:

  • Detailed scans of brains cells in Parkinson’s disease patients revealed that patients who received placebos (in the form of a salt solution) responded in the same way and with the same level of relief as they would in receiving a drug to relieve their symptoms. This study, performed at the University of Turin Medical School in Italy, discovered that the placebo effect caused a release of dopamine, a lack of which causes Parkinson’s patients’ tremors and muscle rigidity. (Published in Nature Neuroscience, 2004.)
  • People who suffer from depression and receive a placebo not only usually improve, but a section of their brain linked to memory and attention becomes activated; this same brain area is repressed as a side effect when the patients take anti-depressant drugs. “People who get better on placebo have a change in brain function just as surely as people who get better on medication,” said Andrew Leuchter of the University of California at Los Angeles, who led the nine-week study of fifty-one patients. “We now know that placebo is very definitely an active treatment condition.” (Published in The American Journal of Psychiatry, 2001.)

Fitzgerald, Randall. The Hundred-Year Lie: How to Protect Yourself from the Chemicals That Are Destroying Your Health (pp. 190-191). Plume. Kindle Edition.