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Functional somatic syndrome
Medical condition

Functional somatic syndrome (FSS) refers to a group of conditions characterized by chronic symptoms without an identifiable organic cause. Among these, Fibromyalgia is the most common, while ME/CFS is also widely recognized as an FSS condition, despite controversy from some patient groups. These syndromes are highly prevalent, yet their causes remain largely unknown. The absence of biological markers complicates diagnosis, which is typically made by excluding other medical conditions. Understanding and categorizing FSS remains a challenge in medical science due to these limitations.

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Definition and Terminology

FSS refers to disturbances in bodily functioning where aetiology is unknown,8 including that psychogenesis is not assumed.9

Related terms

"Medically unexplained physical symptoms" include FSS situations, but also situations where the symptoms are sporadic and where psychogenesis may be suspected.10

"Persistent physical symptoms"11 includes FSS situations but also situations where persistent physical symptoms are caused by a known illness, such as arthritis.

In somatic symptom disorder chronic physical symptoms, which may or may not be linked to a known illness, coincide with excessive and maladaptive thoughts, emotions, and behaviors connected to those symptoms. In FSS these features are not present.

Classification

This term does not appear in the ICD-11.

Signs and symptoms

Functional somatic syndromes are characterized by ambiguous, non-specific symptoms that appear in otherwise-healthy people. Overlap in symptomology exists across diagnoses, including gastrointestinal issues, pain, fatigue, cognitive difficulties, and sleep difficulties. Some have proposed to group symptoms into clusters1213 or into one general functional somatic disorder given the finding of correlations between symptoms and underlying etiologies.1415

Pre-diagnosis contact with health systems

A large (n = 43,676) 2020 study found that 5 years prior to diagnosis, FSS patients consulted more frequently for a range of psychological and somatic conditions than did controls. Around half this cohort were ME/CFS patients (normally not termed an FSS).16

FSS conditions

FSS disorders include

Overlap of FSS conditions

A large overlap of symptoms exist between the FSS diagnoses, causing high rates of comorbidity between them; the prevalence of comorbid FSS diagnoses ranges from 20% to 70%, while comorbid affective disorders with a fibromyalgia diagnosis ranges from 20% to 80%.28

Prevalence

Studies have found prevalence in the general population of having at least one FSS of 16.3% (n = 9656),29 and 9.3% (n = 3054).30

Some 10% of the general population, and around 33% of adult patients in clinical populations, suffer from functional somatic symptoms.31

Comorbidity

PTSD

Rates of PTSD are roughly 9.5–43.5% higher in people seeking treatment for a functional somatic syndrome as opposed to the general population.32

Potential causes

Psychological factors

Patients with somatic syndromes such as fibromyalgia and irritable bowel syndrome have significantly higher rates of both physical and sexual abuse prior to the onset of their physiological symptoms, as well as higher rates of previous emotional abuse, emotional neglect, and physical neglect compared to the general population.33 Further, childhood trauma such as sexual abuse or maltreatment can indicate an increased propensity for later somatic syndrome onset.

"Attentional bias" has been posited as the psychological mechanism by which trauma and somatic symptoms are tied.3435 The concept of attentional bias refers to the idea that traumatic events can cause individuals to become more attuned to their bodies, thus intensifying the perception of pain, fatigue, and other common somatic symptoms.36 The initial traumatic event is interpreted as a threat to the body, and therefore the stress-response of the body takes on a new, heightened awareness to any potential subsequent threats. This attentional bias leads to a "health anxiety," where the patient becomes increasingly concerned that common somatic symptoms are related to a physical disease or injury, and therefore, another potential bodily threat.37 An initial perception of lost control can further lead to this attentional bias; sense of control is negatively associated with symptom reporting, suggesting that somatic symptoms are more closely monitored when psychologically recovering from an incident of lost control.38 Functional Somatic Syndromes are thought to be a result of conditioned hyperarousal following a trauma; victims are conditioned to respond more sensitively to the somatic symptoms following a trauma by their attention to and reinforcement of the symptom existence. This feedback loop is similar to that of panic disorder, in which fear of a subsequent panic attack causes an increased hyper-vigilance towards, and exacerbation of, certain physiological symptoms, such as heart palpitations, dizziness, and breathlessness.39

Biological factors

One hypothesis implicates the hypothalamic–pituitary–adrenal axis (HPA axis) in the manifestation of somatic symptoms following trauma. The HPA axis plays a major role in moderating the body's stress response to both emotional and physical pain, relating to both the experience of psychological symptoms prevalent following trauma as well as the physiological symptoms prevalent in FSS conditions.40 When an individual experiences a traumatic event, the HPA-axis causes the increased release of cortisol, activating the sympathetic nervous pathway and causing negative feedback to be sent to the hypothalamus and pituitary gland. In people who have experienced significant trauma, this reaction can become dysfunctional and can cause a chronic decrease in cortisol production, though the rates of this decrease in cortisol levels varies across different types and frequencies of trauma.41

Diagnosis

Diagnosis of a FSS is usually a diagnosis of exclusion, where physicians rule out other disorders that could explain the dysfunctions being experienced.42

Management and Treatment

CBT can be helpful for FSS. Medications such as antidepressants may play a role.4344

History

The term functional somatic syndrome was used in a 1999 paper.45

References

  1. Geraghty KJ, Esmail A (2016-08-01). "Chronic fatigue syndrome: is the biopsychosocial model responsible for patient dissatisfaction and harm?". British Journal of General Practice. 66 (649): 437–438. doi:10.3399/bjgp16X686473. ISSN 0960-1643. PMID 27481982. https://bjgp.org/content/66/649/437 ↩

  2. Barsky AJ, Borus JF (1999-06-01). "Functional somatic syndromes". Annals of Internal Medicine. 130 (11): 910–921. doi:10.7326/0003-4819-130-11-199906010-00016. ISSN 0003-4819. PMID 10375340. https://pubmed.ncbi.nlm.nih.gov/10375340 ↩

  3. Donnachie E, Schneider A, Enck P (2020-06-17). "Comorbidities of Patients with Functional Somatic Syndromes Before, During and After First Diagnosis: A Population-based Study using Bavarian Routine Data". Scientific Reports. 10 (1): 9810. doi:10.1038/s41598-020-66685-4. ISSN 2045-2322. PMC 7299983. https://www.nature.com/articles/s41598-020-66685-4 ↩

  4. Fink P, Schröder A (May 2010). "One single diagnosis, bodily distress syndrome, succeeded to capture 10 diagnostic categories of functional somatic syndromes and somatoform disorders". Journal of Psychosomatic Research. 68 (5): 415–426. doi:10.1016/j.jpsychores.2010.02.004. ISSN 1879-1360. PMID 20403500. https://pubmed.ncbi.nlm.nih.gov/20403500 ↩

  5. Linde A (2007-10). "[Chronic fatigue syndrome--a functional somatic syndrome]". Therapeutische Umschau. Revue Therapeutique. 64 (10): 567–574. doi:10.1024/0040-5930.64.10.567. ISSN 0040-5930. PMID 18214210. {{cite journal}}: Check date values in: |date= (help) https://pubmed.ncbi.nlm.nih.gov/18214210 ↩

  6. Henningsen P, Zimmermann T, Sattel H (2003). "Medically unexplained physical symptoms, anxiety, and depression: a meta-analytic review". Psychosomatic Medicine. 65 (4): 528–533. doi:10.1097/01.psy.0000075977.90337.e7. ISSN 1534-7796. PMID 12883101. https://pubmed.ncbi.nlm.nih.gov/12883101 ↩

  7. Wessely S, Nimnuan C, Sharpe M (1999-09-11). "Functional somatic syndromes: one or many?". Lancet (London, England). 354 (9182): 936–939. doi:10.1016/S0140-6736(98)08320-2. ISSN 0140-6736. PMID 10489969. https://pubmed.ncbi.nlm.nih.gov/10489969 ↩

  8. Donnachie E, Schneider A, Enck P (2020). "Comorbidities of Patients with Functional Somatic Syndromes Before, During and After First Diagnosis: A Population-based Study using Bavarian Routine Data". Scientific Reports. 10 (1): 9810. Bibcode:2020NatSR..10.9810D. doi:10.1038/s41598-020-66685-4. PMC 7299983. PMID 32555301. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7299983 ↩

  9. Mayou R, Farmer A (August 3, 2002). "Functional somatic symptoms and syndromes". BMJ. 325 (7358): 265–268. doi:10.1136/bmj.325.7358.265. PMC 1123778. PMID 12153926 – via www.bmj.com. https://www.bmj.com/content/325/7358/265.full ↩

  10. "Medically unexplained symptoms". nhs.uk. October 19, 2017. https://www.nhs.uk/conditions/medically-unexplained-symptoms/ ↩

  11. Löwe B, Toussaint A, Rosmalen JG, Huang WL, Burton C, Weigel A, et al. (June 15, 2024). "Persistent physical symptoms: definition, genesis, and management". The Lancet. 403 (10444): 2649–2662. doi:10.1016/S0140-6736(24)00623-8. PMID 38879263 – via www.thelancet.com. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)00623-8/fulltext ↩

  12. Fink P, Schröder A (May 2010). "One single diagnosis, bodily distress syndrome, succeeded to capture 10 diagnostic categories of functional somatic syndromes and somatoform disorders". Journal of Psychosomatic Research. 68 (5): 415–426. doi:10.1016/j.jpsychores.2010.02.004. PMID 20403500. /wiki/Doi_(identifier) ↩

  13. Lacourt T, Houtveen J, van Doornen L (January 2013). ""Functional somatic syndromes, one or many?" An answer by cluster analysis". Journal of Psychosomatic Research. 74 (1): 6–11. doi:10.1016/j.jpsychores.2012.09.013. PMID 23272982. https://doi.org/10.1016%2Fj.jpsychores.2012.09.013 ↩

  14. Wessely S, White PD (August 2004). "There is only one functional somatic syndrome". The British Journal of Psychiatry. 185 (2): 95–96. doi:10.1192/bjp.185.2.95. PMID 15286058. https://doi.org/10.1192%2Fbjp.185.2.95 ↩

  15. Teodoro T, Oliveira R (October 2023). "The conceptual field of medically unexplained symptoms and persistent somatic symptoms". CNS Spectrums. 28 (5): 526–527. doi:10.1017/S1092852922001031. hdl:10362/147363. PMID 36321347. S2CID 253256995. /wiki/Doi_(identifier) ↩

  16. Donnachie E, Schneider A, Enck P (June 17, 2020). "Comorbidities of Patients with Functional Somatic Syndromes Before, During and After First Diagnosis: A Population-based Study using Bavarian Routine Data". Scientific Reports. 10 (1): 9810. Bibcode:2020NatSR..10.9810D. doi:10.1038/s41598-020-66685-4. PMC 7299983. PMID 32555301. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7299983 ↩

  17. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  18. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  19. Afari N, Ahumada SM, Wright LJ, Mostoufi S, Golnari G, Reis V, et al. (January 2014). "Psychological trauma and functional somatic syndromes: a systematic review and meta-analysis". Psychosomatic Medicine. 76 (1): 2–11. doi:10.1097/PSY.0000000000000010. PMC 3894419. PMID 24336429. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3894419 ↩

  20. Mayou R, Farmer A (August 2002). "ABC of psychological medicine: Functional somatic symptoms and syndromes". BMJ. 325 (7358): 265–268. doi:10.1136/bmj.325.7358.265. PMC 1123778. PMID 12153926. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1123778 ↩

  21. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  22. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  23. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  24. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  25. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  26. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

  27. "2.2 The Putative Disappearance of Somatic Manifestations of Hysteria", From Photography to fMRI, transcript Verlag, pp. 219–237, 2022-12-31, doi:10.1515/9783839461761-009, ISBN 978-3-8394-6176-1, In the late 1990s, it became a matter of heated debate if hysteria's nosological successors were conceptually and diagnostically distinguishable from a range of possibly related clinical conditions that were equally characterised by the lack of any demonstrable physical abnormality. Jointly referred to as functional somatic syndromes, these conditions include multiple chemical sensitivity, sick building syndrome, chronic fatigue syndrome, fibromyalgia, irritable bowel syndrome, chronic whiplash, chronic Lyme disease, the Gulf War syndrome, food allergies, hypoglycaemia. To this date, the delineation between present-day forms of hysteria and other functional somatic syndromes remains unresolved. 978-3-8394-6176-1 ↩

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  45. Barsky AJ, Borus JF (June 1, 1999). "Functional somatic syndromes". Annals of Internal Medicine. 130 (11): 910–921. doi:10.7326/0003-4819-130-11-199906010-00016. PMID 10375340 – via PubMed. https://pubmed.ncbi.nlm.nih.gov/10375340 ↩