Reaction to Placebo Effect May Be Genetic


Acupuncture therapy

The reason why some people tend to respond to treatments that have no active ingredients might be down to genetics. A new study indicates that the placebo effect could be linked to a genetic component.

The scientists published their findings in the journal PLoS ONE. The placebo effect was examined in 104 patients with irritable bowel syndrome (IBS). Those with a particular version of the COMT gene saw an improvement in their health after placebo acupuncture, in which the needles never pierced the skin.


Placebo sugar pills. Image by Best Raw Organic.

It’s hoped that these findings will be seen in other conditions. The study sample is small, and independent replications are needed to determine if this phenomenon applies just to IBS or to all diseases, or to different classes of infections and/or ailments.

Generally speaking, the placebo effect is seen when a patient experiences an improvement in their condition while undertaking a treatment that is inert, like taking a sugar pill or placebo acupuncture. The patient believes that the needles are going into their skin, but they aren’t.

There isn’t a single placebo response and a single mechanism, states Fabrizio Benedetti of the University of Turin Medical School. Two groups in this study received different treatment. One received theirs in a business-like clinical manner, while the other received it from a warm, supportive practitioner. A third group received no treatment at all.

After three weeks, the patients were asked if they had seen an improvement in their IBS. The team used blood samples to look at what variant the individual had of the catechol-O-methyltranferase (COMT) gene, which plays a role in the dopamine pathway.

This gene was chosen because there had been increasing evidence that the neurotransmitter dopamine is activated when people anticipate and respond to placebos. Individuals with a COMT variant that tripled the amount of dopamine in the front of the brain felt no improvement without treatment but an improvement with placebo acupuncture.

However, dopamine might not be the only chemical involved in the placebo effect. Previous studies indicate that serotonin is also associated with it.

Reference: “Catechol-O-Methyltransferase val158met Polymorphism Predicts Placebo Effect in Irritable Bowel Syndrome” by Kathryn T. Hall, Anthony J. Lembo, Irving Kirsch, Dimitrios C. Ziogas, Jeffrey Douaiher, Karin B. Jensen, Lisa A. Conboy, John M. Kelley, Efi Kokkotou and Ted J. Kaptchuk, 23 October 2012, PLoS ONE.
DOI: 10.1371/journal.pone.0048135

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