Placebos occupy a pretty weird place in the world of medicine. They get results, and yet contain no actual medicine. They can work even when we know we’re getting them, although just how well they work may depend on your DNA.

We tend to assume that the people who get better after using placebos are dupes, and that the effects are strictly psychological. The reality is so much more complicated than that. As Joe Hanson explains in this video from PBS’s “It’s Okay to Be Smart,” placebo treatments can produce actual physiological changes in patients, causing the brain to release chemicals that can decrease pain and even ease some of the symptoms of Parkinson's disease. 

And not all placebos are created equal—far from it. Everything from a placebo's medium (tablet, pill, or injection) to its coloring and packaging can affect its efficacy. "Clearly," says Hanson, "the critical ingredient in a placebo is expectation."

Check out the video to find out how placebo treatments started, what they’re made of, and why they’ve been giving the pharmaceutical industry so much trouble lately.

Header image via It's Okay to Be Smart, YouTube.