Fibromyalgia Comes in 3 Shapes and Sizes Oct. 3, 3003 -- Mood problems have traditionally been thought to be among the most common fibromyalgia symptoms. But now researchers are saying that psychological disturbances are actually found in only a small number of patients.

Researchers identified three distinct subtypes of fibromyalgia symptoms and found higher than normal levels of distress, anxiety, and other psychological disturbances to be present in only one of the groups.

"The problem is that this subgroup, which was in the minority in our study, tends to color the perceptions about all fibromyalgia patients," study co-researcher Daniel J. Clauw, MD, tells WebMD. "We found that the majority of fibromyalgia patients didn't have these psychological factors that explained their pain."

Fibromyalgia Symptoms Vary

It is believed that 3.7 million Americans have fibromyalgia -- a poorly understood disorder characterized by widespread pain and tenderness that cannot be traced to a specific physical cause. Women are far more likely to be diagnosed with the condition than men, and it often occurs with other unexplained disorders such as irritable bowel syndrome and chronic fatigue.

Researchers have long suspected that there are multiple causes for the chronic pain and other fibromyalgia symptoms.

"It seems obvious that this is more than one disease, but because we don't understand it very well we are lumping everyone with chronic widespread pain together and calling it fibromyalgia," Clauw says.

Clauw and colleagues attempted to identify defining fibromyalgia symptoms in their study of 97 patients, published in the October issue of the journal Arthritis and Rheumatism. The 85 women and 12 men were subjected to a series of physical and psychological tests, and the researchers identified three distinct clusters of patients.

3 Clusters of Fibromyalgia Symptoms

Cluster 1 -- 52% of patients

• Moderate levels of anxiety and depression
• Reacting to pain in a way that moderately amplifies distress
• Moderate control over pain
• Highest pain threshold
• Moderate to low tenderness

Cluster 2 -- 32% of patients

• Highest levels of anxiety and depression
• Reacting to pain in a way that severely amplifies distress
• Lowest control over pain
• Considerable tenderness

Cluster 3 -- 16% of patients

• Lowest levels of anxiety and depression
• Reacting to pain in a way that minimally amplifies distress
• Highest control over pain
• Lowest pain thresholds
• Highest level of tenderness