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An individual's threshold for pain is often called pain sensitivity. For years, researchers believed that pain sensitivity was determined by one's genes, making it inflexible. Now, according to a new study out of King's College London, new evidence suggests that pain sensitivity could be affected by one's lifestyle and environment. This is the first study to conclude that the genes tied to pain sensitivity could be turned on or off by lifestyle and environmental factors.

"Epigenetic switching is like a dimmer switch for gene expression. This landmark study shows how identical twins, when combined with the latest technology to look at millions of epigenetic signals, can be used to find the small chemical switches in our genes that make us all unique - and in this case respond to pain differently," Tim Spector, Professor of Genetic Epidemiology at King's College London, said.

For this study, the researchers examined pain sensitivity in identical twins and compared it to unrelated individuals. Since identical twins share 100 percent of their genes, their pain sensitivity should be the same and any differences would be caused by lifestyle and environmental factors. The researchers first tested 25 sets of identical twins with a heat probe. The probe was placed on their arms and they were instructed to press a button when the heat became intolerable. The team used DNA sequencing to analyze more than five million epigenetic marks across the whole genome. They then compared the results with 50 unrelated individuals.

Based from their analysis, the researchers found significant differences in one particular gene tied to pain sensitivity between the identical twins. The findings suggest that the gene, TRPA1, could be turned on or off by the environment or by lifestyle.

"The potential to epigenetically regulate the behavior of TRPA1 and other genes involved in pain sensitivity is very exciting and could lead to a more effective pain relief treatment for patients suffering with chronic pain," lead author of the study, Dr. Jordana Bell, from the Department of Twin Research & Genetic Epidemiology at King's College London, stated.

The findings were published in Nature Communications.