Background/Purpose: Fibromyalgia was first defined by rheumatologists, and is often thought of as a disorder of widespread pain and decreased pain threshold. In the wider literature, however, including non-US studies, fibromyalgia is considered to be one of a series of “medically unexplained syndromes.” These illnesses are sometimes called somatic symptom disorders (SSD) or functional somatic syndromes because the main symptoms, pain, fatigue, cognitive disturbance, and unrefreshed sleep, are somatic and have no clear etiological explanation. This definition, however, comes into conflict with the Diagnostic and Statistical Manual-5 (DSM) of SSD mental illnesses draft criteria of April-27-2012. DSM-5 defines a SSD as a mental illness when all of A and B are present chronically: A) one or more somatic symptoms that are distressing and/or result in significant disruption in daily life; B) persistently high level of anxiety about health or symptoms OR excessive time and energy devoted to these symptoms or health concerns.

Methods : We studied 13,229 rheumatic disease patients, including 3,657 who satisfied ACR 2010 criteria for fibromyalgia modified for survey research and 9,572 who did not meet criteria. We calculated the criteria Symptom Severity score (SS4) and omitted the non-somatic depression symptom of SS4. We defined patients as probably DSM-5 positive if they had at least one of the following symptoms, fatigue, cognitive disturbance, unrefreshed sleep present which was defined at a severity level of “Severe: continuous, life-disturbing problems.”  DSM-5 status was defined as definite if they had at least 2 of the 3 symptoms at a severe level or had an average SS4 of at least 10 of a possible 12.

Results : See Table 1. 35.0% of FM positive patients were positive at a definite level, 2.6% of non-FM criteria patients were positive. Probable DSM positivity in FM patients was indicated by 39.3% with severe fatigue scores, 42.2% with severe unrefreshed sleep, and 15.8% with severe cognitive problems.

Conclusion : Using severity measures from survey modified ACR 2010 fibromyalgia criteria, we noted high rates of DSM-5 SSD positivity. At least 35% of FM patients would be classified as having an SSD mental disorder using our definitions. These results are inconsistent with clinical experience and call into question the use of proposed DSM criteria in clinical populations. Moreover, many, including us, would argue that all FM patients have an SSD, though not necessarily a mental disorder. Our results should be regard with caution because our definitions used ad hoc measures based on FM assessments, and it is possible that different levels of abnormalities might have been found using the Whitely Index mentioned in DSM-5. However, such an index is not used outside of psychiatric clinics and does not appear germane to FM symptoms. The DSM-5 continues to be revised.

Percent satisfying DSM-5 criteria