Why some people develop chronic pain: It’s all in the head
Scientists have uncovered new information about why some people develop persistent and long-term pain; yet others with the same type of injury don’t. In a first study, researchers have found that it’s a combination of the injury and the state of the brain that leads to chronic pain.
Strong emotional response to injury predicts chronic pain
It took ten years of research to uncover what happens in the brain that allows some people to recover after an injury heals, while others continue to hurt.
The Northwestern University Feinberg School of Medicine investigation found that chronic pain starts when two specific areas of the brain communicate with each other. The more the two areas ‘talk’ to each other, the greater likelihood that chronic pain will develop.
For the study, researchers looked at brain imaging in 40 people with back pain and found they could predict with 85% accuracy who would go on to develop chronic pain, depending on the level of communication between the frontal cortex and the nucleus accumbens brain regions.
The participants were all diagnosed with an initial episode of back pain that persisted for 4 to 16 weeks. Brain scans were performed at the start of the study and three more times during a 12-month period.
A. Vania Apakarian, senior author of the paper and professor of physiology at Northwestern explained in a press release, "The injury by itself is not enough to explain the ongoing pain. It has to do with the injury combined with the state of the brain.
It may be that these sections of the brain are more excited to begin with in certain individuals, or there may be genetic and environmental influences that predispose these brain regions to interact at an excitable level."
The more emotionally charged the brain is when the injury occurs, the greater the likelihood a person will experience chronic pain.
The finding is important because treating pain costs $600 billion a year, according to a 2011 National Academy of Sciences report, with back pain being the most common condition.
Pain that persists after an injury has healed is difficult to treat because there isn’t any intervention that is scientifically proven to work.
Apkarian explains that the nucleus accumbens is responsible for ‘teaching’ the rest of the brain. When an injury occurs, it may be telling the rest of the brain to develop chronic pain.
The study also showed that people with chronic pain lose gray matter, meaning they have fewer neurons that are essential for communication between brain regions.
The study, published in the journal Nature Neuroscience, is the first to show the link between early brain changes and chronic pain. "Now we hope to develop new therapies for treatment based on this finding," Apkarian said. The finding suggests pain that doesn’t go away after an injury heals is literally all in the head. The research finding could help millions in the United States who suffer from chronic unrelieved pain by providing an entirely new treatment approach.
Nature Neuroscience (2012) doi:10.1038/nn.3153
July 1, 2012
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