Pain hurts. But when that pain is ongoing, it does more than just hurt the affected body parts. Chronic pain can make it hard to think or function and can lead to depression and strained relationships. Now researchers have found evidence that prolonged exposure to pain can even alter DNA in the brain and immune system. They published their findings last week in the journal Scientific Reports.
The National Institute of Neurological Disorders and Stroke estimates that more than 100 million Americans live with chronic pain. But despite its prevalence and devastating consequences, chronic pain is still not very well understood.
The authors of the latest study wondered if the effects of prolonged pain could reach the genetic level. They examined DNA from the brains and white blood cells of both healthy rats and rats recovering from nerve injuries. The researchers focused on tracking the chemicals called methyl groups, which are considered a good indicator of changes in gene expression.
They expected to find at least a few altered genes in the DNA of the pain group. They found a whole lot more than that. "We were surprised by the sheer number of genes that were marked by the chronic pain—hundreds to thousands of different genes were changed," study co-author Moshe Szyf said in a press statement.
Many of those genes were in areas of the brain associated with cognitive issues, depression, and anxiety. "We found that chronic pain changes the way DNA is marked not only in the brain but also in T cells, a type of white blood cell essential for immunity," Szyf continued in the press statement. "Our findings highlight the devastating impact of chronic pain on other important parts of the body such as the immune system. We can now consider the implications that chronic pain might have on other systems in the body that we don't normally associate with pain."
As Szyf and his colleagues emphasize in their paper, these findings have "very broad implications." Still, it’s important to keep in mind that these experiments were performed on rats, not humans. Further studies will be needed to confirm these results and explore their relationship to the human experience of pain.