[Fibromyalgia and anxiety disorder.]

The etiology of fibromyalgia is unclear. The diagnosis is based on widespread pain and muscular tenderness, but other symptoms often occur, such as sleep disturbance, excessive anxiety and fatigue and concentration difficulties. All these symptoms can occur in generalized anxiety disorder. The aim of this study was to assess whether fibromyalgia is associated with other diagnoses, particularly anxiety disorder.

The study includes all those receiving full disability pension on the 1st of December 2001 as ascertained by the disability register at the State Social Security Institute of Iceland. Information was obtained from the register on gender, age and diagnoses of the disability beneficiaries. Diagnoses were compared between two groups of disability beneficiaries - an index group with fibromyalgia and a comparison group without that diagnosis. There were 716 women in each group. We also compared diagnoses among the women who had fibromyalgia as primary diagnosis in the index group and among all women who had anxiety/depression as primary diagnosis.

In the index group fibromyalgia was the single registered diagnosis in only 6.8% of cases, while 38.3% of the comparison group had a single registered diagnosis. There was a significant difference between the two groups in terms of the number of diagnoses by disease category (p<0.0001). Among individual categories of disease, the only category that showed a significant excess in the index group was mental disorders (p<0.0001). Women with fibromyalgia as a primary diagnosis were compared with women with a primary diagnosis of anxiety or depression in terms of distribution of the numbers of diagnoses per person. The distribution pattern was similar.

The probability of having a mental disorder, especially an anxiety disorder, is significantly higher amongst women with fibromyalgia as compared to other women with full disability pension. This indicates an association between fibromyalgia and anxiety, an association which needs to be properly addressed in the treatment of this disorder.