What high rates of physical and mental comorbidity remind us about fibromyalgia

This journal recently published a paper by Sleurs et al., entitled ‘Comorbidities of self-reported fibromyalgia in United States adults: A cross-sectional study from The National Epidemiological Survey on Alcohol and Related Conditions (NESARC-III). (Sleurs, Tebaka, Scognamiglio, Dubertret, & lLe strat, 2020)’. While its primary message is that persons reporting a physician diagnosis of fibromyalgia have very high rates of physical and mental comorbidities, this study provides other important information on the nature and validity of fibromyalgia and fibromyalgia diagnosis, as it is likely the most of the reported fibromyalgia patients in the study would not satisfy criteria for fibromyalgia. In the clinic, diagnosis of fibromyalgia is in ‘the eye of the beholder’. Close to 20 years ago George Ehrlich observed that ‘no one has FM until it is diagnosed’—that diagnosis is arbitrary. A striking result of the Sleurs et al. epidemiological study is the observation that 87.5% of those with reported fibromyalgia are women, confirming results from other population derived estimates of physician diagnosed fibromyalgia. In contrast, population-based studies applying current published criteria have found that around 60% or fewer fibromyalgia patients are women (Häuser, Brähler, Ablin, & Wolfe, 2020). In addition, we know from multiple studies that most clinically diagnosed patients do not satisfy criteria for fibromyalgia, and in a recent population study only 14.6% of persons who satisfied published criteria for fibromyalgia had received a clinical diagnosis of fibromyalgia (Häuser et al., 2020). Presumably, had such persons been interviewed in the Sleurs et al. study they would not have been included as fibromyalgia patients. Data such as these underscore problems of fibromyalgia definition and diagnosis. Fibromyalgia can be an arbitrary diagnosis. It appears to be diagnosed disproportionally in women and almost never thought of in men and, if multiple studies are correct, most community diagnosed fibromyalgia patients may not even satisfy fibromyalgia criteria. In studies where published criteria are applied, many patients diagnosed with one set of criteria will not be the same as those diagnosed with another set (Häuser et al., 2020)? Readers might reasonably ask, ‘What is fibromyalgia’? Do other characteristics, such as sex, mental symptoms and social factors influence the diagnosis and definition of fibromyalgia? This study throws light on another important issue. What are we to make of the extremely high rates of mental illness and physical comorbidity in those with fibromyalgia in this study? One hundred percent of reported fibromyalgia cases had at least one physical disorder, 68% had four or more disorders, 67% reported ‘arthritis’ and 80% were found to have a mental disorder. Some might try to separate these patients into primary of secondary fibromyalgia groupings, though it would seem clear that trying to guess the specific causal path would be hazardous. According to the authors, ‘The strengths of the relationships between mental disorders and self-reported fibromyalgia in our study support the hypothesis of central sensitization in fibromyalgia’. However, readers should be aware that current knowledge does not allow for the fibromyalgia sensitization hypothesis to be falsified, and mental and physical illness could be the cause or result (or some mixture) of fibromyalgia—a disorder that has no gold standard and whose definition has changed repeated over the last 60 years. We recently reported a similar study of self-reported physical and mental comorbidities in 12,215 patients in a research databank (Wolfe, Ablin, Guymer, Littlejohn, & Rasker, 2020), and obtained results similar to those of this study. Using a criteria-based definition of fibromyalgia as well as the quantitative measure of fibromyalgia severity, the polysymptomatic distress (PSD) scale, we found that criteria-based fibromyalgia as well as PSD were associated with an increase in the number of comorbidities. In addition, we found the association of PSD was present above and below the fibromyalgia diagnostic cut point. That is the degree of fibromyalgia-like symptom severity is more important than the presence or absence of fibromyalgia. Readers should also know that patients with fibromyalgia in this study are likely to satisfy diagnoses that fall under the rubric of bodily distress and other functional somatic syndromes. The main difference between these syndromes and fibromyalgia is the organizational beliefs and medical specialties of those making diagnoses and performing research. Considering fibromyalgia symptoms quantitatively with the PSD avoids the problems inherent with diagnostic and selection bias. In addition, it sidesteps the issue of central sensitivity attributions associated with diagnosis since if applies to the entire spectrum of patient symptom severity. No one argues about fibromyalgia symptoms. Instead the controversy regarding fibromyalgia is how to classify and understand the symptoms and their social meaning. It is unfortunate that the authors of this very important current study were unable to administer the PSD, as it would have further defined the nature of comorbidity in symptomatic patients. We advise that this simple scale—which also provides a fibromyalgia diagnosis for those who require it—be used in future similar studies. None declared. None declared.