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Expectations can relieve pain

Interventions that induce expectations can be effective for relieving patients’ pain. This finding is promising for optimising the effectiveness of treatments, conclude Kaya Peerdeman and colleagues in their recently published meta-analysis. 

The placebo effect and expectations

Peerdeman and her co-researchers conducted a meta-analysis, a method that combines the results of multiple studies. Previous studies have shown that expectations are important predictors of the outcome of analgesic (pain-relieving) treatments. Expectations can be influenced by verbal suggestions, conditioning or mental imagery. Participants in these studies, for example, receive a treatment with or without the suggestion that it is a powerful analgesic. Conditioning involves the pairing of, for example, a placebo pill with reduced pain stimulation, after which the placebo itself can cause pain relief. An example of mental imagery is imagining feelings of pain-relieving warmth in painful areas. 

Verbal suggestion most promising

Research on this type of interventions has been conducted mostly in healthy subjects. To investigate how well these findings translate to the clinic, Peerdeman and colleagues have now summarised the existing knowledge of the effects of expectation interventions on patients’ pain. The meta-analysis showed that brief expectation interventions can effectively relief various types of pain, like chronic back pain, recurrent migraine, or surgery pain. Verbal suggestion demonstrated the most promising effects. An example of such a verbal suggestion is: ‘The agent you have just been given is known to powerfully reduce pain in some patients’. Less studies were conducted in the area of conditioning and mental imagery that both showed overall small to medium effects. The effects also varied depending on the type of pain, with the largest effect for pain caused by a medical procedure (e.g., surgery). 

Optimising treatment effectiveness

These findings show that expectation interventions are promising for optimising the effectiveness of standard analgesic treatments in clinical practice. Most notably, the observed effects underline the importance of the information a clinician provides when administering an analgesic treatment. Informing patients about, and emphasising, the positive intended and expected outcomes of an analgesic intervention, without neglecting possible negative side effects, can optimise treatment effectiveness. 

Peerdeman is a PhD candidate in Prof. dr. Andrea Evers’ research group at Leiden University. This research was funded by Evers’ NWO Vidi grant.

Relieving patients’ pain with expectation interventions: a meta-analysis was published in the June 2016 issue of PAIN, a leading journal in pain research. 

Kaya Peerdeman was interviewed about this study. You can listen to this radio interview (in Dutch) on the NPO Radio 1 Nieuws en co website.

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