Genes determine whether sugar pills work

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Genes determine whether sugar pills work

http://www.eurekalert.org/pub_releases/2008-12/uu-gdw120308.php

It is a well-known fact in drug trials that individuals can respond

just as well to placebos, sugar pills, as to the active drug. On the

other hand, it is difficult to explain why only certain people get

better from placebos. A team of researchers from Uppsala University

and Gothenburg University have now found gene variants that can

impact the placebo effect and a mechanism in the brain that

characterizes those who respond to placebos.

The study, published in Journal of Neuroscience, examined 108

individuals suffering from social phobia using a brain camera (PET,

positron emission tomography). The individuals were participating in

a treatment study looking into how anxiety-moderating drugs affect

brain activity. Just under one fourth of the subjects were given a

placebo instead of a drug. This was a double-blind study, meaning

that neither the subjects nor the research team know who was taking

the drug or the sugar pill.

Before and after an eight-week period of treatment, the participants

were asked to give a stressful oral presentation while their brain

activity was monitored. When all the metering was finished and the

study was decoded, it turned out that 40 percent of the placebo group

had received the same degree of anxiety relief from the sugar pill as

other groups got from a drug.

Those who responded well to the placebo had a significant reduction

in activity in the amygdala in the temporal lobe, while this

reduction was not found in the others. In previous research the

amygdala has stood out as a key structure for emotional reactions.

Both serotonin-active drugs (SSRI preparations) and cognitive

behavioral therapy moderate activity in this area.

" Thus, successful placebo treatment works through the same mechanism

in the brain, " says Tomas Furmark at the Uppsala University

Department of Psychology, who directed the study.

The study also analyzed two genes that influence the reabsorption and

synthesis of serotonin in the brain (the serotonin transporter gene

and the tryptophan hydroxylase-2 gene). The findings showed that only

individuals who had certain variants, alleles, of these genes had a

moderation of activity in the amygdala. Above all, the tryptophan

hydroxylase-2 genes variants could predict the degree of relief from

anxiety achieved by the placebo pill as well as the moderation of the

amygdala.

Statistical analyses showed that it is a genetic effect on the

activity in the amygdala that influences the propensity to respond to

a placebo, that is, a path from the gene, via the brain, to behavior.

The study shows for the first time that genes influence the placebo

effect by regulating the propensity to react in an area of the brain

that is important for our feelings.

This could have significant consequences for all drug testing and

other treatment studies that use a placebo.

" The findings show that the possibilities of demonstrating that an

active treatment functions better than a placebo can be affected by

the gene variants in the trial subjects. It is also possible that

genes can explain why certain people respond well or poorly to

anxiety-moderating drugs and psychotherapy respectively, " says Tomas

Furmark.