Previous expectations can influence how much pain people eventually feel. These expectations can be shaped by external cues or by verbal information from clinicians about how treatments might relieve pain. Led by Lauren Atlas, researchers from the National Institute of Health explored if and how distinct ways of shaping expectations differentially influence physically hurtful experiences.
In their JNeurosci paper, the researchers present their findings from 40 healthy volunteers who rated how hurt they were following painful heat stimulation during neuroimaging scans. Participants learned external cues for pain, which varied from trial to trial. For some trials, participants also received placebo "treatment" lotion. External cues alleviated pain for all participants, but only half the participants reported hurting less with the introduction of the placebo treatment. The researchers also found that predictive cues were less impactful when patients were also given placebo treatment. The combined effects of cues and treatment were linked to activity in several distinct brain regions. There were separate neural associations with the effects of external cues alone or placebo lotion alone; only external cues affected a brain biomarker for pain, and treatment expectations influenced evaluative brain areas. Thus, expectations shaped by external cues or information about treatments may have different mechanisms for influencing pain.
According to the researchers, this work suggests that cue-based expectations have more consistent effects than treatment-based expectations, which clinicians may need to keep in mind. Says Atlas, "If a doctor says, 'This is going to hurt,' that is a cue. When a doctor explains, 'This treatment is going to relieve your pain,' that is a different type of expectation. Doctors may need to know that the way they inform patients will have different impacts on how much pain they feel."
