Have you ever taken phenylephrine for a stuffed-up nose and then felt better? If so, you might have been perplexed when Food and Drug Administration experts recently said that that the drug — which is in some versions of DayQuil, Sudafed, and other medicines — is no more effective than a placebo. But to Michael H. Bernstein, an assistant professor of diagnostic imaging at the Warren Alpert Medical School of Brown University, it all makes sense. On this episode, Bernstein discusses the placebo effect and its counterpart, the “nocebo effect.”