Verbal reports of pain and suffering in ischemic pain produced by a tourniquet to the upper arm followed by exercise of the occluded hand were studied in eight highly hypnotizable college undergraduates under conditions of normal wakefulness, hypnosis without anesthesia, and hypnosis with suggested anesthesia.
Subjects were able to distinguish between felt sensory pain and the concomitant suffering in verbal reports on numerical scales. Suggestions of hypnotic anesthesia reduced both sensory pain and suffering (in "open" reports) about 90% in the group as a whole, and eliminated both completely for three subjects. However, "hidden" reports of pain and suffering during hypnotic anesthesia, obtained through automatic talking, were not significantly different from those obtained in the hypnosis without anesthesia condition.
The existence of two cognitive systems, processing information at dissociated levels of awareness, was proposed. The results, while puzzling, are interpreted as not casting doubt on the clinical effectiveness of hypnosis in pain reduction.
Knox VJ, Morgan AH, Hilgard ER. Pain and Suffering in IschemiaThe Paradox of Hypnotically Suggested Anesthesia as Contradicted by Reports From the "Hidden Observer". Arch Gen Psychiatry. 1974;30(6):840-847. doi:10.1001/archpsyc.1974.01760120090013