Genetic sequencing is revealing
that the placebo response is actually a complex phenotype. The study of genomic
effects on the placebo response, referred to as “the placebome”, has yielded
ample evidence that genetic variations in the brain’s neurotransmitter pathways
modify placebo effect. The placebo effect occurs when patients show improvement
from treatments that contain no active ingredients. Scientists initially used
behavioral instruments such as personality measures to predict which patients
would respond to placebos. Over the past decade, the development of
neuroimaging technologies illuminated the activation of the brain's
neurotransmitter pathways in response to placebos. Because they are the
chemical messengers that either excite or inhibit nerve function in the brain,
many neurotransmitters play key roles in reward and pain. Researchers from Beth
Israel Deaconess Medical Center have hypothesized that genetic variation in the
genes that encode the proteins in these neurotransmitter pathways might also
modify placebo responses. In 2012 the first placebo biomarker,
catechol-O-methyltransferase (COMT), was identified by Kathryn T. Hall. Genetic
variations in the COMT gene influences the brain’s levels of the
neurotransmitter dopamine which also determined the extent of an individual’s
placebo response. Researchers reviewed scientific literature over the last 10
years and were provided with confirmation that, beyond the COMT gene, there is
evidence for genetic variation in other neurotransmitter pathways that modify
placebo response.
This research suggests that the
assumptions of placebo controls in randomized clinical trials need to be
reconsidered. The next step in describing the placebome would be to include a
no-treatment control in placebo-controlled randomized clinical trials. I found
this article to be interesting as it sheds new light on what is known about the
placebo effect. I’m curious to see how further research on this topic effects
clinical trials and the use of placebos.
http://www.sciencedaily.com/releases/2015/04/150413140906.htm
http://www.webmd.com/pain-management/what-is-the-placebo-effect
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