How Expecting the Worst Can Make You Sick

You Should Know: Lauding the “power of positive thinking” is almost a cliché at this point. You might not know, however, that the flip side can be just as powerful. The “nocebo effect” occurs when negative expectations about a treatment lead to real negative outcomes, including side effects that the treatment itself isn’t actually causing.

Going Deeper: When you expect something bad to happen, your brain releases a hormone that can worsen both anxiety and pain sensitivity. In one study, patients receiving continuous pain medication reported a major increase in pain the moment they were told it stopped, even though it hadn’t. Past treatment experiences (think starting a new medication after a previous one failed) can also prime your brain to expect the worst since it processes past experiences through regions tied directly to pain perception.

Takeaway: What a clinician says during treatment can also affect how your body responds. And people who tend to be more anxious or pessimistic appear more vulnerable to nocebo responses.

Bottom Line: Expecting to feel worse might actually make you feel worse in the long run.