Classifying Fibromyalgia Syndrome as a Mental Disorder?-An Ambulatory Assessment Study.

Purpose: Fibromyalgia syndrome (FMS) is associated with psychological distress. The recent revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) raises the question of whether FMS is classifiable as "somatic symptom disorder" (SSD) and consequently as a mental disorder. To address this, the present ambulatory assessment study focuses on the everyday life occurrence of SSD symptoms in FMS and their predictive value concerning severity indicators of widespread pain.

Method: Ambulatory data were assessed six times daily on 14 consecutive days via iPod. Twenty-eight women suffering from FMS indicated symptoms associated with SSD (somatic illness beliefs, health anxiety, time/energy devoted to pain, or health concerns) and momentary pain levels. Questionnaires regarding potential covariates (such as somatization, depression, health status) were completed at two additional sessions in the research laboratory.

Results: On average, SSD symptoms occurred three to four times daily and were mild to moderate in severity. Furthermore, these symptoms were both concurrently and prospectively associated with momentary pain intensity and subjective impairment by pain. Twenty percent of the variance in pain intensity and 28 % of the variance in subjective impairment were explained by momentary variables (SSD symptoms and intake of pain medication). Eighty-two percent of persons with FMS fulfilled the psychological SSD criterion when considering everyday occurring symptoms with at least mild severity.

Conclusion: FMS might be diagnosed as a mental disorder according to DSM-5 in many cases. SSD symptoms proved to have predictive value for FMS severity and may thus have clinical relevance for diagnostic, prognostic, and intervention purposes.