It’s well known that expectations, positive or negative, can strongly influence how much pain people feel. For instance, if you expect an injection will hurt a lot, it’s more likely to do so, even if the needle poke is relatively minor.
That’s what a brain-imaging study in Nature Human Behaviour has confirmed—that expectations of pain intensity can not only become self-fulfilling prophecies, but that expectations can persist even when experience repeatedly demonstrates they are unfounded. Negative expectations can result in what researchers call the nocebo effect, the flipside of the placebo effect, both of which can influence the efficacy of a drug or other medical treatment.
Neuroscientists at the University of Colorado at Boulder recruited 28 people, ages 18 to 55, who were taught to associate one visual cue (a symbol or the words “low” or “high”) with high painful heat and another with low heat. Then the participants were placed in a functional MRI machine to measure their brain activity while low or high heat was repeatedly applied to their forearm or leg. Before each application they were shown a low or high cue, and after each they were asked to rate their pain. They didn’t know that the cues did not predict the intensity of the heat application.
The MRI scans showed that when participants were shown the high-heat cue, brain regions involved in fear and threat were more activated. And when they received the heat, they perceived and reported more pain after seeing a high-heat cue, regardless of the level of heat they actually received—and, most important, this also influenced their perception of subsequent heat applications. Similarly, low heat cues led to less perceived pain. That is, participants’ expectations strongly influenced how their brains processed pain and limited their ability to learn from experience.
As the senior author stated, because of the reciprocal feedback loop between expectation and pain, “the more pain you expect, the stronger your brain responds to the pain, [and] the stronger your brain responds to the pain, the more pain you expect.”
The mind/body connection is a key to pain and many other aspects of health. When people are ill, negative expectations may interfere with recovery by amplifying their perceived pain, even after damaged tissue has healed, and may prevent them from noticing that they are feeling better. In particular, persistent negative expectations “may facilitate the transition from acute to chronic pain, which is all too common after surgery or injury,” the authors noted.
Being aware of negative expectations and the power they can exert—even when evidence contradicts them—may help you revise them and, in doing so, alter your perceived experience in ways that speed recovery. Better yet, err on the side of positive expectations.
This article first appeared in the UC Berkeley Wellness Letter.
Also see 10 Habits for Managing Chronic Pain.