Tests Prove Fibromyalgia is Not Depression

by Kristin Thorson, Fibromyalgia Network Editor
Posted: September 30, 2010

Fibromyalgia can be distinguished from depression, according to a new study by researchers at the University of Sherbrooke in Canada.

People with fibromyalgia not only have widespread pain, a large percentage also battles depression. This has led some investigators to argue that fibromyalgia might represent a form of depression, but pain system function tests prove otherwise.

The Canadian research team evaluated three groups of subjects: 40 healthy controls, 26 depressed patients, and 29 fibromyalgia patients. All participants were asked to determine when a heat probe changed from a warm sensation to pain. The ability of the body to reduce the impact of pain was also measured.

Prior studies by the corresponding author Serge Marchand, a professor in the department of surgery at the University of Sherbrooke in Canada, have shown that the body’s natural ability to inhibit pain in fibromyalgia patients does not work. When the body is subjected to a lot of discomfort, the central nervous system should pour out pain relieving substances. This does not happen in people with fibromyalgia, but what about those with depression?

The temperature that healthy subjects rated the heat probe as painful was much higher than the ratings for fibromyalgia patients. The depressed subjects fell in between these two groups, so they do have some evidence of increased pain sensitivity.

Looking at the system that helps keep pain under control, the healthy and depressed groups both produced a similar response that led to pain relief. This same system did not work at all in the fibromyalgia patients.

According to Marchand, “this result shows that fibromyalgia can be distinguished from major depressive disorder.” The system in the body that helps block out pain works efficiently in depressed patients, but fails to function in people with fibromyalgia.

Fibromyalgia patients often struggle with symptoms of depression, and depressed patients report various pain complaints, such as headaches and back pain. Marchand suspects this overlap in symptoms may be related to the increased pain sensitivity in both groups. Despite this similarity, he emphasizes that the fibromyalgia patients were significantly more heat sensitive.

Source: Normand E, et al. “Pain Inhibition Is Deficient in Chronic Widespread Pain but Normal in Major Depressive Disorder” Journal of Clinical Psychiatry 2010; DOI: 10.4088/JCP.08m04969blu.

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