Mirrors can alleviate arthritis

Swapped-hand illusion produces drop in pain ratings, preliminary study shows

WASHINGTON — Tricking people with severe arthritis into thinking their sore hand is healthy dampens their pain, a new study suggests.

If confirmed, the preliminary results may offer a powerful and inexpensive way to fight persistent arthritis pain. 

“The results are really exciting,” said pain expert Candy McCabe of the University of Bath in England, who wasn’t involved in the study. “The whole thing is visual trickery, but the science behind it is strong.”

The new technique, described November 12 at the annual meeting of the Society for Neuroscience, is a type of mirror therapy, in which the illusion of a pain-free hand makes people feel better. So far, visual feedback from mirrors has been shown to reduce some kinds of chronic pain, notably the pain felt in  “phantom limbs” of amputees. But it was unclear whether mirror therapy could reduce pain produced by arthritic, inflamed joints.

In the new work, Laura Case, V.S. Ramachandran and colleagues at the University of California, San Diego recruited eight volunteers who had osteo- or rheumatoid arthritis. The volunteers saw a reflection of Case’s healthy hand in the same place where their sore hand should have been. To strengthen the sensation of the hand-swap, the researchers simultaneously touched Case’s hand and the volunteer’s hand, creating a unified sensation of seeing and feeling the touch. The volunteer then mimicked a series of slow hand movements made by the researcher.

After experiencing the illusion, volunteers reported a reduction in pain by an average of about 1.5 points on a 10-point scale, with 10 being the worst pain possible. Some people’s pain ratings dropped as much as three points, Case said.

“What it tells us is the power of vision,” McCabe said. “In this case, vision is somehow overriding what we think of as the strongest sense — pain.”

Usually, mirror therapy is done with a person’s own healthy hand. But since both of the participants’ hands were swollen and appeared painful, the team used healthy hands from the experimenter. Simply seeing a gnarled, sore hand might have a profound effect on feeling pain, Case said. 

Because the current experiment tested pain only immediately before and after the illusion, the researchers don’t know whether the method could produce lasting relief. The results are preliminary, Case emphasized, and the team plans to conduct more studies to figure out the most effective form of treatment.

If the results are confirmed, the method may offer a cheap and effective way of alleviating chronic arthritis pain, without the side effects of drugs. “This is something that is easily accessible,” McCabe said. “No matter where in the world you are, there are mirrors.”

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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