The findings suggest that interventions designed to reduce pain-related fear and anxiety, such as behavioral therapy, should play a bigger role in the treatment of chronic arthritis pain, the study's researcher tells WebMD.
"Most arthritis patients don't have access to these types of therapies, or if they do, they tend to get them after they have lived with pain for many years," says neuro-rheumatologist Anthony K.P. Jones, MD. "We believe patients would fare better if they were treated with these therapies much earlier."
The Pain Systems
The study by Jones and colleagues from the University of Manchester Rheumatic Diseases Center is the first to directly examine how the brain processes arthritis pain using a specific type of brain imaging.
Two parallel areas within the brain have been identified as pain processing centers -- the lateral system and the medial system.
While both systems share many of the same functions, earlier work by the University of Manchester research team identified the medial system as being more involved in the emotional aspects of pain, such as fear and stress.
The lateral system was found to be more involved in processing sensory aspects of pain, such as pain location and duration.
Studies involving healthy volunteers subjected to controlled pain made it clear that the way people think about their pain can change their perception of it, Jones says.
"That may sound obvious, but a lot of people with pain think they have no control over what they are feeling," he says. "The fact is that the brain rules in terms of pain perception."
In their latest study, the researchers attempted to determine if people with chronic pain respond in a similar way.
Six women and six men with knee osteoarthritis (OA) were recruited for the trial. Brain imaging was performed when the subjects were experiencing arthritis pain, when they were pain-free, and when they were experiencing controlled, heat-related pain to the arthritic knee administered by the researchers.
For all 12 patients, both types of pain activated both pain systems. But activity within the medial system was much greater when the patients were experiencing arthritis pain.
The findings suggest that for these patients, arthritis pain was more strongly associated with fear and distress than other types of pain. The study appears in the April issue of the journal Arthritis and Rheumatism.
The fact that high concentrations of natural opiates are found in the medial pain system has implication for researchers searching for new drugs to treat arthritis and other chronic pain conditions, Jones says.
"Drugs that enhance naturally occurring opiates may have fewer side effects than synthetic opiates like morphine," he tells WebMD.
Nondrug treatments designed to teach patients how to better perceive and cope with their pain also target the medial system.
The brain-imaging research is not the first to find that positive thinking can influence the perception of chronic pain.
In a 2005 study conducted at Wake Forest University, volunteers were subjected to similar levels of experimental pain. But those trained to perceive the pain as minimal reported much lower pain levels than those trained to expect severe pain.
More importantly, they also showed less pain-related activity on brain scans.
"Expectations of decreased pain powerfully reduced both the subjective experience of pain and activation of pain-related brain regions," Wake Forest neuroscientist Robert Coghill, PhD, says in a press release.