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Fibromyalgia — Overview

TL;DR — Fibromyalgia (FM) is a chronic disorder defined by widespread musculoskeletal pain plus fatigue, non-restorative sleep, and cognitive difficulty, affecting roughly 2–4% of the general population when measured by criteria (Häuser 2015, PMID 27189527; Clauw 2014, PMID 24737367). It has become the paradigm case of "nociplastic pain," the third mechanistic pain descriptor added beside nociceptive and neuropathic pain in 2016 (Kosek 2016, PMID 26835783; Fitzcharles 2021, PMID 34062144), and it anchors the ICD-11 category of chronic primary pain (Treede 2019, PMID 30586067). Its burden is large — healthcare costs ~3× matched controls (Berger 2007, PMID 17655684), roughly one in five patients unable to work (Choy 2010, PMID 20420681), elevated suicide risk despite unremarkable overall mortality (Wolfe 2011, PMID 20662040) — yet its mechanism, its boundaries as a diagnosis, and even its status as a discrete entity remain genuinely unresolved (Wolfe & Walitt 2013, PMID 23820862; Sarzi-Puttini 2020, PMID 33024295). That combination — common, disabling, mechanistically open — is what makes the field scientifically consequential.

What fibromyalgia is

The core clinical picture is chronic widespread pain accompanied by physical exhaustion, unrefreshing sleep, and cognitive difficulties ("fibrofog") (Häuser 2015, PMID 27189527). Patients typically report many concurrent symptoms — in an 8-country survey, a mean of 7.3 of 14 queried symptoms, with pain, fatigue, sleep problems and concentration difficulty the most common (Choy 2010, PMID 20420681). Tenderness to pressure (historically formalized as "tender points"), stiffness, headache, irritable bowel symptoms, paresthesias, and mood symptoms are frequent accompaniments, documented since the first controlled clinical study in 1981 (Yunus 1981, PMID 6944796).

Three features define the scientific problem:

  1. No objective marker. Diagnosis rests entirely on symptom report and examination; no laboratory, imaging, or physiological test is validated for diagnosis (Galvez-Sánchez 2020, PMID 32340369). See biomarkers.
  2. Definition by committee, repeatedly revised. The case definition changed materially in 1990, 2010, 2011, 2016, and 2019, and each revision changes who counts as a case — including the apparent sex ratio (Jones 2015, PMID 25323744). See diagnostic criteria.
  3. Continuum behavior. Population data show FM-defining features (pain extent, tenderness, distress) distributed smoothly across the population rather than clustering as a discrete disease, a finding reported both by external epidemiologists (Croft 1994, PMID 7950521) and by the lead author of the ACR criteria himself (Wolfe 1997, PMID 9166001; Wolfe 2013, PMID 23424058). See history and nosology.

The nociplastic-pain framing

In 2016 an IASP task force proposed a third mechanistic descriptor for chronic pain states that are neither clearly nociceptive (driven by tissue damage/inflammation) nor neuropathic (driven by a somatosensory lesion) (Kosek 2016, PMID 26835783). The term adopted was nociplastic pain: pain arising from altered nociception — augmented CNS pain and sensory processing and altered pain modulation — without clear evidence of tissue or nerve damage sufficient to explain it (Fitzcharles 2021, PMID 34062144). Fibromyalgia is consistently presented as the prototype: multifocal pain more widespread or intense than expected from peripheral findings, accompanied by CNS-derived symptoms (fatigue, sleep, memory, mood), and comparatively unresponsive to peripherally directed therapies such as NSAIDs, opioids, surgery, or injections (Fitzcharles 2021, PMID 34062144). Clinical criteria and a grading system ("possible" vs "probable" nociplastic pain) for nociplastic pain affecting the musculoskeletal system were published by an IASP expert group in 2021 (Kosek 2021, PMID 33974577).

Two related classification moves consolidated this framing. First, the IASP classification for ICD-11 created chronic primary pain — pain as a disease in its own right, persisting >3 months with significant distress or disability and not better accounted for by another condition — and explicitly places fibromyalgia in this subgroup (Treede 2019, PMID 30586067; Nicholas 2019, PMID 30586068). Second, US taxonomy work (AAPT) produced a multidimensional diagnostic framework for FM within chronic pain disorders generally (Arnold 2019, PMID 30453109).

The framing has critics: the original proposal drew the published objection that a third descriptor was premature — "not yet" — given the absence of a validated mechanism or test (Granan 2017, PMID 27984528), and the descriptor is explicitly a clinical label, not a demonstrated pathophysiology (Kosek 2016, PMID 26835783). The mechanistic evidence for and against central amplification is treated in central pathophysiology and the peripheral counter-case in peripheral pathophysiology; the debate over the concept itself is in history and nosology.

Burden

Criteria-based prevalence is roughly 2% of adults in population studies (1.78% pooled general-population estimate, 95% CI 1.65–1.92, Heidari 2017, PMID 28447207; 2.1% in Germany, Wolfe 2013, PMID 23424058; 1.75% ≈ 3.94 million US adults, Walitt 2015, PMID 26379048), with clinic-facing reviews citing 2–8% depending on criteria (Clauw 2014, PMID 24737367). Annual healthcare costs run about three times those of matched controls (mean $9,573 vs $3,291; median 5× higher; Berger 2007, PMID 17655684), with total direct annual costs per patient estimated at $1,750–$35,920 in the USA and $1,250–$8,504 in Europe (2019 USD) (D'Onghia 2022, PMID 35849890). In an 8-country patient survey, 22% were unable to work and another 25% could not work consistently (Choy 2010, PMID 20420681); US population data likewise show high medical costs, Social Security and work disability among criteria-positive persons (Walitt 2015, PMID 26379048). Overall mortality is not clearly elevated (SMR 0.90, 95% CI 0.61–1.26 in 8,186 patients; Wolfe 2011, PMID 20662040), but death by suicide is consistently over-represented (suicide OR 3.31, 95% CI 2.15–5.11, Wolfe 2011, PMID 20662040; female suicide SMR 10.5, 95% CI 4.5–20.7 in a Danish cohort, Dreyer 2010, PMID 20583101; pooled suicide SMR 3.37, 95% CI 1.52–7.50, Treister-Goltzman 2023, PMID 37429737). Quantitative detail lives in epidemiology.

Key numbers at a glance

Quantity Estimate Criteria/population Source (PMID)
General-population prevalence (pooled) 1.78% (95% CI 1.65–1.92) Meta-analysis, mixed criteria 28447207
Prevalence range across criteria, same population 1.7% (ACR 1990) / 1.2% (2010) / 5.4% (modified 2010) NE Scotland 25323744
Female share of cases ≈59–60% (unbiased, 2016 criteria) vs >90% (referred/diagnosed samples) Databank + population reanalysis 30212526
Undiagnosed fraction among criteria-positive adults 73% US NHIS 2012, surrogate 2011 criteria 26379048
Time from first presentation to diagnosis Mean 2.3 years, 3.7 physicians 8-country patient survey 20420681
Annual healthcare costs vs matched controls $9,573 vs $3,291 (mean, ~3×) US claims 17655684
Unable to work due to FM 22% 8-country patient survey 20420681
All-cause mortality SMR 0.90 (95% CI 0.61–1.26) 8,186 US patients, 35 yr 20662040
Suicide mortality OR 3.31 (95% CI 2.15–5.11); pooled SMR 3.37 (1.52–7.50) US cohort; meta-analysis 20662040; 37429737

Why the field matters scientifically

FM sits at the intersection of several open problems. It is common and disabling, yet its mechanism is explicitly unresolved: the leading model — biological and psychosocial variables interacting to predispose, trigger, and aggravate a chronic illness — is acknowledged even by its proponents to be unclear in its details (Häuser 2015, PMID 27189527), and etiopathogenesis, criteria, and classification all remain debated (Sarzi-Puttini 2020, PMID 33024295). It functions as the reference condition for "centralized" pain states, so mechanistic findings in FM propagate to chronic low back pain, tension-type headache, IBS, and the broader family of overlapping conditions (Clauw 2014, PMID 24737367; Fitzcharles 2021, PMID 34062144; Yunus 2007, PMID 17350675) — see comorbidities and overlap. And it is a live case study in nosology: whether medicine should carve a discrete disease out of a population continuum of pain and distress is contested with data on both sides (Croft 1994, PMID 7950521; Wolfe 2013, PMID 23424058), while under- and over-diagnosis coexist at scale in the community (Walitt 2015, PMID 26379048; Wolfe 2019, PMID 30724039). A validated mechanism or biomarker would settle much of this at once; none exists (Galvez-Sánchez 2020, PMID 32340369).

Map of the topic

How FM came to be defined, the contested-illness history, and the continuum debate are in history and nosology; the full criteria genealogy (ACR 1990 → 2010 → 2011 → 2016, AAPT 2019, ICD-11) with performance data is in diagnostic criteria; prevalence, incidence, delay, costs, and mortality are in epidemiology. Mechanism is split across central pathophysiology (sensitization, neuroimaging, descending inhibition), peripheral pathophysiology (small-fiber and muscle findings), and autoimmunity and inflammation (IgG transfer work, cytokines); predisposition and triggers are in genetics and risk factors. Symptom-domain science is in sleep, fatigue, cognition and comorbidities and overlap. Treatment evidence is split into pharmacologic therapy and non-pharmacologic therapy, with society recommendations compared in guidelines. Measurement problems that shape every trial are in outcomes and measurement; the search for objective tests in biomarkers and omics and emerging science; the trial pipeline in clinical-trials landscape; and the lived-experience and legitimacy dimension in patient experience and advocacy.

Open questions

  • Is FM one condition, several, or the severe tail of a population continuum? Dimensional analyses find no natural cut-point (Wolfe 2013, PMID 23424058; Croft 1994, PMID 7950521), yet the diagnosis behaves clinically as a category — no study has yet arbitrated with modern latent-structure methods at population scale.
  • Does the nociplastic descriptor pick out a mechanism or merely a clinical phenotype? The grading criteria exist (Kosek 2021, PMID 33974577) but the objection that the category is premature has not been empirically answered (Granan 2017, PMID 27984528).
  • Why is criteria-based FM so often clinically invisible (73% of criteria-positive US adults undiagnosed; Walitt 2015, PMID 26379048) while clinic diagnosis is simultaneously often criteria-negative (Wolfe 2019, PMID 30724039)? What does each population actually share?
  • Can the elevated suicide signal (Wolfe 2011, PMID 20662040; Treister-Goltzman 2023, PMID 37429737) be decomposed into psychiatric comorbidity vs pain-specific risk, and is it modifiable?

References

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  2. Clauw DJ. Fibromyalgia: a clinical review. JAMA. 2014;311(15):1547-55. PMID 24737367
  3. Kosek E, et al. Do we need a third mechanistic descriptor for chronic pain states? Pain. 2016;157(7):1382-1386. PMID 26835783
  4. Fitzcharles MA, et al. Nociplastic pain: towards an understanding of prevalent pain conditions. Lancet. 2021;397(10289):2098-2110. PMID 34062144
  5. Kosek E, et al. Chronic nociplastic pain affecting the musculoskeletal system: clinical criteria and grading system. Pain. 2021;162(11):2629-2634. PMID 33974577
  6. Treede RD, et al. Chronic pain as a symptom or a disease: the IASP Classification of Chronic Pain for the International Classification of Diseases (ICD-11). Pain. 2019;160(1):19-27. PMID 30586067
  7. Nicholas M, et al. The IASP classification of chronic pain for ICD-11: chronic primary pain. Pain. 2019;160(1):28-37. PMID 30586068
  8. Arnold LM, et al. AAPT Diagnostic Criteria for Fibromyalgia. J Pain. 2019;20(6):611-628. PMID 30453109
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  12. Galvez-Sánchez CM, Reyes del Paso GA. Diagnostic Criteria for Fibromyalgia: Critical Review and Future Perspectives. J Clin Med. 2020;9(4):1219. PMID 32340369
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  20. Walitt B, et al. The Prevalence and Characteristics of Fibromyalgia in the 2012 National Health Interview Survey. PLoS One. 2015;10(9):e0138024. PMID 26379048
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