Chronic back pain is linked to physical changes in the brain, according to researchers in Germany.
Chronic back pain can cause misery to sufferers
A team found patients with the condition also had microstructural changes in the pain-processing areas of their brains.
The scientists said the work provided evidence that the condition was real and it could aid treatment research.
The research was presented at the Radiological Society of North America's annual meeting, in Chicago.
To study the condition, the researchers used a technique called diffusion tensor imaging (DTI) to look at the differences between sufferers' and healthy volunteers' brains.
They discovered the brains of patients with chronic back pain had a more complex and active microstructure compared with the healthy volunteers' brains.
The changes occurred in regions of the brain associated with pain-processing, emotion and stress response.
Cause or result?
Lead researcher Dr Jurgen Lutz, a radiologist at Ludwig-Maximilians University in Munich, Germany, said: "A major problem for patients with chronic pain is making their condition believable to doctors, relatives and insurance carriers. DTI could play an important role in this regard.
"With these objective and reproducible correlates in brain imaging, chronic pain may no longer be a subjective experience. For pain diagnosis and treatment, the consequences could be enormous."
However, the researchers said more research would be needed to determine whether the physical changes were a cause or result of the pain.
Co-author Gustav Schelling, from the Department of Anaesthesiology at Munich University, said: "It's difficult to know whether these are pre-existing changes in the brain that predispose an individual to developing chronic pain, whether ongoing pain creates the hyperactivity that actually changes the brain organisation, or if it is some mixture of both.
"DTI may help explain what's happening for some of these patients, and direct therapeutic attention from the spine to the brain."
Dr Alison McGregor, a back pain expert from Imperial College London, said: "Eighty percent of the population suffer from back pain at some point in their lives, and quite often you cannot find a physical cause for that."
She said the study added to a growing body of research that revealed chronic pain was associated with physical changes in the brain.
"We are gradually getting more of an understanding on whether the central nervous system is involved in back pain - however we are not really sure what the physical changes mean."