But new research suggests a placebos can even help relieve the symptoms of a serious neurological disorder, like Parkinson's disease.
Experiments by Professor Jon Stoessl, director of the Pacific Parkinson's Research Centre at the University of British Columbia, in Vancouver, have shown placebo pills can be highly effective in minimizing the symptoms of Parkinson's. But Stoessl's research doesn't just rely on observation and patient interviews. He has scanned patients' brains to find out just what's going on.
"What we found is that in somebody with Parkinson's disease, a placebo can release as much dopamine as amphetamine or speed can in somebody with a healthy dopamine system," Stoessl told BBC News. "So it's a very dramatic response."
What that means, is that placebos don't just distract a patient or help him or her better cope with their symptoms. They actually trigger the brain to release chemicals the body needs to allay -- at least momentarily -- the malady.
Professor Tor Wager at the University of Colorado has been conducting similar research.
"When we've given people a placebo treatment what we see is the release of endogenous opioids, which is the brain's own morphine," Wagner told the BBC. "What that means is that the placebo effect is tapping into the same pain control circuitry as opiate drugs like morphine."
So far, the research shows how powerful the placebo effect is, able to tap into the pharmacies inside our brains -- and get it to produce the same chemicals that are sold in pill form. But scientists are still working toward learning how to harness this power.
The body of research surrounding the placebo effect is growing, but it is still in its infancy. Regardless, researchers are encouraged.
"The placebo effect is real, quantifiable and in fact you're doing quite well with an active therapy if you can get as good a response as the placebo response," said Stoessl.