A longitudinal brain imaging study tracking participants suffering from back injuries claims chronic pain may - quite literally - be in the patient’s head.
"For the first time we can explain why people who may have the exact same initial pain either go on to recover or develop chronic pain," explained Professor A. Vania Apakarian of Northwestern University.
"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. This finding is the culmination of 10 years of our research."
According to Apakarian, the more emotionally the brain reacts to the initial injury, the more likely the pain will persist after the injury has healed.
"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," he said.
Apakarian also noted that the nucleus accumbens is an important center for teaching the rest of the brain how to evaluate and react to the outside world. To be sure, this brain region may use pain signals to instruct the rest of the brain to develop chronic pain.
Interestingly enough, chronic pain participants in the study also lost gray matter density, which is likely linked to fewer synaptic connections or neuronal and glial shrinkage (brain synapses are essential for communication between neurons).
"Chronic pain is one of the most expensive health care conditions in the US yet there still is not a scientifically validated therapy for this condition," said Apkarian. Indeed, chronic pain costs an estimated $600 billion a year, with back issues weighing in as the most prevalent chronic pain condition.
A total of 40 participants who had an episode of back pain that lasted 4-16 weeks, but with no prior history of back pain, were closely observed in the above-mentioned study. Brain scans were conducted on each participant when the study initially kicked off, followed by three more visits during the course of a year.