How will a placebo affect you?

A genetic marker of placebo therapy susceptibility has been found

ABC MagazineDespite the fact that placebo drugs have been actively used in clinical trials for more than 70 years, scientists still do not know exactly why these inactive substances help some patients get rid of symptoms and have absolutely no effect on others.

Researchers from the United States and Israel for the first time managed to detect genetic differences between those who "respond" and "do not respond" to placebo drugs. Perhaps their discovery, published in the journal PLoS ONE (Catechol-O-Methyltransferase val158met Polymorphism Predicts Placebo Effect in Irritable Bowel Syndrome), can explain exactly how the "placebo effect" occurs.

According to researchers from Beth Israel Deaconess Medical Center and Harvard Medical School, scientists already know that the neurotransmitter dopamine plays a significant role in a person's susceptibility to placebo. The more dopamine there is in the brain, the better a person reacts to taking a placebo. Therefore, scientists focused their attention on the gene encoding the enzyme catechol-O-methyltransferase (COMT), which is involved in the formation of dopamine. Due to the phenomenon of polymorphism, there are several variants of this gene — either with two copies of methionine alleles (met/met), or with two copies of valine alleles (val/val), or with one copy of the allele of each amino acid.

As it turned out, people with the met/met variant produce 3-4 times more dopamine than those with other genetic variants. The researchers suggested that such people should respond better to taking a placebo. To test this hypothesis, they analyzed blood samples from participants in a 2008 clinical trial that tested the effectiveness of various treatments for irritable bowel syndrome, including acupuncture as placebo therapy.

Their assumptions were confirmed: met/met variants of the SOMT gene were found in all study participants who responded positively to placebo therapy. Owners of this gene were 6 times more likely to report an improvement in their condition after acupuncture than owners of other genetic variants. Thus, the scientists write, the met/met variant of the SOMT gene can be considered a genetic marker of a positive placebo effect, and the val/val variant can be considered a marker of a zero placebo effect.

The researchers hope that their discovery will especially help researchers conducting clinical trials of drugs with placebo groups. Currently, a new drug needs to demonstrate efficacy several times greater than the placebo effect in order to be approved by the FDA. The ability to predict the placebo effect in research participants in advance will help reduce the scale, cost and duration of clinical trials.

Portal "Eternal youth" http://vechnayamolodost.ru25.10.2012