Hypnotic suggestion — the act of offering an idea for action or for consideration of action— is an empirically validated form of pain control, although exactly how or why it helps to control pain remains unclear.

Using brain scans in fibromyalgia patients under hypnotic induction, researchers found that the technique produces changes in underlying neural activity related to the effects of suggestion, and the mechanism of response in patients differed from that seen in controls — even though their behavioral response was similar. The study, “Suggestions to Reduce Clinical Fibromyalgia Pain and Experimentally Induced Pain Produce Parallel Effects on Perceived Pain but Divergent Functional MRI–Based Brain Activity.” is published in the journal Psychosomatic Medicine.

Targeted suggestions after a hypnotic induction are well-established in clinical practice and have been increasingly used as a research tool in cognitive neuroscience. In particular, several reviews and meta-analyses have demonstrated the efficacy of hypnotically suggested analgesia in reducing chronic pain, acute surgical pain, and acute nonsurgical pain.

Stuart W.G. Derbyshire, PhD, with the NUS Department of Psychology in Singapore, and his colleagues evaluated 13 fibromyalgia patients who received suggestions to alter their clinical pain, and 15 healthy controls who received suggestions to alter experimental heat pain. Suggestions were delivered before and after hypnotic induction, with blood oxygen level–dependent (BOLD) activity measurements taken at the same time. BOLD is a method used in functional magnetic resonance imaging (fMRI) to observe activity in different areas of the brain or other organs.

Both controls and patients reported large changes in pain experience after hypnotic and nonhypnotic suggestions of increasing or decreasing pain experience, although hypnotic suggestions produced larger changes and the added benefit of hypnotic suggestion trended toward significance overall, according to the authors.

Surprisingly, though, BOLD response increased in patients with pain report in regions previously associated with pain, including thalamus and anterior cingulate cortex. In controls, BOLD response decreased with pain report. All changes were greater after hypnotic induction.

According to the authors, “these findings imply that induction has an important effect on underlying neural activity mediating the effects of suggestion … the pattern of BOLD activity in the controls differs substantially from that observed in the patients. That difference implies a very different mechanism of suggestion in controls compared with patients, which would not have been evident from the behavioral data.”