A “sugar pill” or dummy pill, that contains no active medicine. Double-blind studies are considered the best of all in proving whether a new drug works. Say 100 people take a new medicine, and another 100 take an identical-looking pill with nothing in it (placebo). Neither the patients nor the investigators know who gets what, to avoid bias (assignments are random and coded; the code is opened at the end). If 70 people on the real drug seem better, but 70 taking placebo also feel better, we can’t say that the new medicine worked. In fact. I’ve read a study or two showing red placebo works better than blue placebo (I don’t recall the colors per se).
Placebo is not merely psychologically faking someone out. When a person truly believes they’re going to be better from a treatment, chemicals called endorphins and enkephalins are released in the brain. These are opioids, related to morphine (our natural narcotics). So people really do feel better physically. If someone feeling better on placebo is given naloxone (Narcan®), an antidote for opioid poisoning, they quickly feel worse.
So whenever I give a patient medication, and their symptoms improve, they’re happy with my care. I congratulate myself along with them, but always maintain my own intellectual honesty & skepticism. Maybe it wasn’t my medicine that helped them, but simply a placebo effect.
Then there’s “nocebo,” the opposite, when someone experiences harmful effects from an empty pill. Whereas the “pla-” in “placebo” is from Latin for “pleasure,” the “no-” means “harmful” (like “noxious”). There was actually a case of a patient in a study who overdosed on what he thought was an antidepressant, but wound up being placebo. His blood pressure dropped dangerously, but improved when he was told he’d actually taken nothing. Nobody knows how this effect happens. However, it’s common for patients to read about medication side effects, and then begin to experience them. Studies have shown this to occur.
I never give patients placebo intentionally, because to me that’s dishonest. However, there are many medicines we use that personally I’m not at all convinced are truly effective. Nonetheless, they’re standard acceptable treatments, and I use them. Are they just placebos? Who knows?!?