The power of placebos has long been known. People who believe that they are taking an effective drug frequently feel better. In fact, prior to the discovery of penicillin, it is likely that the placebo effect accounted for much of the benefit of medical care.

A study published in the journal Neurology makes an interesting connection between the magnitude of the placebo effect and the medication’s perceived price.

The study enrolled 12 patients with moderate to severe Parkinson’s disease. They were told that they were going to be given two new injectable medications for Parkinson’s that increase dopamine levels. They were told that the medications were believed to work equally well, but because of differences in how they are manufactured one medicine costs $100 per dose while the other costs $1,500 per dose.

The patients were randomized as to which medication they received first: the cheap or the expensive one. The patients received objective measurements of their ability to move and other Parkinson’s symptoms before and after the medication dose. The measurements were made by people who didn’t know which medication the patient received. About four hours after the first medication they received the other medication, again with symptom measurement before and after.

What the patients didn’t know is that both injections were just saline, salt water without any active ingredient.

Not surprisingly, the patients improved after both injections. What was surprising was that the expensive placebo was much more effective than the cheap one. In terms of magnitude of effect, the expensive placebo was about halfway between the cheap placebo and the effect of levodopa, a Parkinson’s medication that actually increases dopamine levels in the brain.

The result would have been less surprising if the patients were told that the more expensive medicine was more effective, but they were told that they were thought to be equally effective and the difference in price was attributed to a difference in manufacturing. Still, we can’t help but fool ourselves into making “you get what you pay for” into a self-fulfilling prophecy. The patients expected a greater effect from the more expensive medicine and actually had more improvement in their motor function.

This may help explain why we spend so much on things we should know won’t help. It may explain the continued success of the vitamin and supplement industry and the preference of some patients for brand-name rather than generic medications. (Many of my patients boggle when I tell them that my family and I use generic medicines whenever possible.)

Students and fans of behavioral economics likely would have predicted the outcome of this study. Wines with more expensive price tags are known to taste better than the same wine with a cheaper price tag. In fact, the whole art of wine tasting seems to evaporate when experts are blinded about what they are tasting. So we should definitely buy cheap wine (and then fool ourselves by putting big price tags on the bottles).

The clinical applications of this study are not obvious. It’s not ethical to deceive patients, so we can’t just start lying and telling them that their medicines are more effective or more expensive than they really are. But we are reminded again of the power of patient expectations. If we can honestly shape expectations, for example by educating patients about the proven benefits of a medicine, perhaps we can ethically allow our patients to benefit from the placebo effect.

And I’m now surer than ever that I’ll be able to cure more of you as soon as I double my fees.

Albert Fuchs is an internal medicine physician who blogs at his self-titled site, Albert Fuchs, MD.