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Reviewed By Michael Smith, MD on Friday, October 24, 2003

Depression doesn't cause the pain of fibromyalgia, a new study shows. But clinical depression can deepen a fibromyalgia patient's experience of pain.

The findings come in a report by Thorsten Giesecke, MD, to this weeks' annual scientific meeting of the American College of Rheumatology. Giesecke is a member of the University of Michigan research team, led by Daniel J. Clauw, MD, using state-of-the-art technology to study fibromyalgia.

"People still doubt fibromyalgia is a disease," Giesecke tells WebMD. "Previously, we found that fibromyalgia patients really do have increased central pain processing. Now we can show this is not affected by depression. Something is wrong here, and it is not at all connected with depression."

The pain of fibromyalgia is one thing. But patients also face the pain of not being taken seriously, notes Roland Staud, MD, director of the musculoskeletal pain research center at the University of Florida, Gainesville. Staud reviewed the study for the ACR program committee.

"Due to the fact that very few physical abnormalities are present in these patients, bias has occurred. Many people think mood abnormalities play a major role," Staud tells WebMD. "Giesecke's group looked at brain responses to painful stimuli, and then checked to see if there was any difference between depressed and nondepressed fibromyalgia patients. They showed the activation of areas of the brain related to pain were not different in patients with and without depression." But there is a difference between people with and without fibromyalgia, he says.

Seeing Pain in the Brain
The researchers use an imaging device called functional magnetic resonance imaging, or fMRI, to look at how the brain responds to pain. Study participants get a mildly painful pressure on their thumb, which makes the brain's pain centers "light up" on the image. Thumb pressure -- at a level healthy people hardly feel -- sets off a firestorm in the pain centers of fibromyalgia patients' brains.

This showed that fibromyalgia pain is real. But some researchers still think this heightened sensitivity to pain is the result of a psychological process -- depression, perhaps. To check this out, Giesecke and colleagues rated 30 fibromyalgia patients on a scale of depression symptoms, then gave them the fMRI thumb-pain test. The result: Depression -- even clinical depression -- had no relation to how the pain centers of the patients' brains reacted to experimental pain.

"All you can say here is the depressed and nondepressed fibromyalgia patients processed the stimulus in an identical way," Staud says. "Depressed fibromyalgia patients do have more clinical pain, we know this."

A Link Between Depression and Pain
Seven of the 30 fibromyalgia patients turned out to be suffering from true clinical depression, as well as fibromyalgia. And while their pain centers responded just like those of other fibromyalgia patients, these depressed patients did indeed have something else going on in their brains.

Depressed fibromyalgia patients responded to pain in two extra brain areas not involved in pain sensation. These parts of the brain -- the anterior insula and the amygdala -- are involved in emotional responses. While they don't appear to affect the sensation of a particular pain, they can deepen the experience of pain.

"The anterior insula is involved in a lot of emotional things that tell you how you feel," Giesecke says. " It is not usually associated with depression, but with the experience of adverse stimuli like bad smells and pictures of faces with fearful expressions. This seems to be a key area that responds to a pain stimulus but also responds to depression."

Depression, it seems, doesn't make fibromyalgia pain more intense. But it may add something unpleasant to the experience of pain. "Pain is mostly determined by the intensity of the pain stimulus and the unpleasantness occurring along with the stimulus," Staud says. "The imaging showed that most of the unpleasantness of the sensation is in these areas that contribute to these feelings. That is very important to the experience of pain."

The findings, Giesecke suggests, may partially explain why some antidepressants are effective in the treatment of pain. And they take researchers a step closer to understanding the mysterious ailment known as fibromyalgia.

"I think the most important point is that fibromyalgia is really a disease," Giesecke says. "I am pretty sure we are on the right track to find the pathophysiology of fibromyalgia. We are getting closer."

SOURCES: Proceedings, American College of Rheumatology Annual Scientific Meeting, Orlando, Fla., Oct. 23-28, 2003. Thorsten Giesecke, MD, research fellow, Chronic Pain Research Center, University of Michigan, Ann Arbor, Mich. Roland Staud, MD, associate professor and director, musculoskeletal pain research center, University of Florida, Gainesville, Fla.

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