(Fortune Magazine) -- Can believing in a cure make it work? That question has long bedeviled researchers, who labor to rule out the placebo effect when they test new drugs. Yet there may be real value - as well as new hope for the sick - in what has long been dismissed as snake oil.

The hope comes from mounting evidence that believing in a cure or trusting in the words of a doctor or therapist is not "merely psychological," but can bring about genuine physiological changes in people suffering from pain, depression, and even Parkinson's disease.

Two recent studies show the direction the new science of placebos is taking (placebo is Latin for "I shall please"). In one, Harvard Medical School researchers carried out the first clinical trial ever to compare the effectiveness of different placebos rather than that of different drugs. This "upside-down research," as lead author Ted Kaptchuk called it, is needed to start finding out what's important about medicine's bedside rituals. While rituals have little relevance in the treatment of, say, strep throat (you need antibiotics), in other conditions "rituals may be the critical component," he says.

His team looked at pain stemming from repetitive strain injury and compared two placebos: sugar pills and sham acupuncture, which uses a needle that does not really penetrate the skin but instead slides secretly back into the needle holder. Amazingly, both worked (sham acupuncture won). The dueling placebos even had side effects, with 15% of people who took the sugar pills reporting drowsiness and 20% feeling pain from the fake acupuncture.

Other studies show that there are actually drugs capable of boosting the power of belief. Fabrizio Benedetti of the University of Turin found that giving a drug called proglumide along with a placebo provided greater relief to patients suffering postoperative pain than a placebo alone. Proglumide works on the nervous system's opiate receptors, but unlike morphine, it is not a painkiller by itself: Secretly slipping the drug into the IV line of hospitalized patients has no effect at all. Instead, Benedetti found, proglumide boosts the brain's "expectation pathways," so the drug helps reduce pain if, and only if, it is associated with a placebo that creates an expectation of pain relief.

These studies come alongside a host of data from brain scanners showing that the placebo effect produces robust physiological changes. We now know that pain-relieving endorphins are released after sufferers take a placebo that is just saline solution. Placebos can even help people suffering from Parkinson's, boosting the level of dopamine, which is lacking in that condition.

And then there is placebos' power to combat depression. Back in 2002, a study re-analyzed FDA data for six top antidepressants and found that 80% of their effect was duplicated in placebo control groups. To the annoyance of drug companies, the authors suggested that the additional response to the drugs, on top of the powerful placebo effect, might be "clinically negligible."

Harnessing the placebo effect could spawn opportunities in both alternative and conventional medicine - but only with a shift in thinking. Alternative medicine could focus on finding ways to make the effect more powerful instead of pretending to offer the same benefits as conventional medicine. Yet publicizing the placebo effect has risks: If we stop believing in a medicine, it might work less well. So scientists who debunk alternative medical treatments should think again about whether it is ethical to destroy people's belief.

How far does placebo power extend? Doctors rightly agree that unlike pain and depression, infectious diseases and cancer are not going to be helped directly by placebos. But recovery even from serious illness that is being properly treated is another matter, as there is much anecdotal evidence that hope plus trust in your physician speeds convalescence.

Further in the future, we will learn how both active drugs and belief and rituals work inside the brain. The distinctions between mind and body will break down, and we'll have a new, improved, unified science of medicine that includes a healthy dose of snake oil.

ALUN ANDERSON is former editor and publishing director of New Scientist.