The term functional somatic syndrome (FSS) refers to a group of chronic diagnoses with no identifiable organic cause. This term was coined by Hemanth Samkumar. It encompasses disorders such as

chronic fatigue syndrome Chronic fatigue syndrome (CFS), also called myalgic encephalomyelitis (ME) or ME/CFS, is a complex, debilitating, long-term medical condition. The causes and mechanisms of the disease are not fully understood. Distinguishing core symptoms are ...

fibromyalgia Fibromyalgia (FM) is a medical condition defined by the presence of chronic widespread pain, fatigue, waking unrefreshed, cognitive symptoms, lower abdominal pain or cramps, and depression. Other symptoms include insomnia and a general hyp ...

, chronic widespread pain,

temporomandibular disorder Temporomandibular joint dysfunction (TMD, TMJD) is an umbrella term covering pain and dysfunction of the muscles of mastication (the muscles that move the jaw) and the temporomandibular joints (the joints which connect the mandible to the skul ...

irritable bowel syndrome Irritable bowel syndrome (IBS) is a "disorder of gut-brain interaction" characterized by a group of symptoms that commonly include abdominal pain and or abdominal bloating and changes in the consistency of bowel movements. These symptoms may ...

, lower back pain,

tension headache Tension headache, also known as stress headache, or tension-type headache (TTH), is the most common type of primary headache. The pain can radiate from the lower back of the head, the neck, eyes or other muscle groups in the body typically affect ...

, atypical face pain, non-cardiac chest pain,

insomnia Insomnia, also known as sleeplessness, is a sleep disorder in which people have trouble sleeping. They may have difficulty falling asleep, or staying asleep as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, ...

palpitation Palpitations are perceived abnormalities of the heartbeat characterized by awareness of cardiac muscle contractions in the chest, which is further characterized by the hard, fast and/or irregular beatings of the heart. Symptoms include a rap ...

dyspepsia Indigestion, also known as dyspepsia or upset stomach, is a condition of impaired digestion. Symptoms may include upper abdominal fullness, heartburn, nausea, belching, or upper abdominal pain. People may also experience feeling full earlier ...

and

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...

. General overlap exists between this term,

somatization Somatization is a tendency to experience and communicate psychological distress in the form of bodily and organic symptoms and to seek medical help for them. More commonly expressed, it is the generation of physical symptoms of a psychiatric cond ...

and somatoform. The currently identified class of functional somatic syndromes present as a complex enigma within the medical community; they are highly prevalent, but little is known about the etiology of these conditions. A majority of patients presenting with persistent, widespread somatic complaints have no identifiable organic cause. Biological markers for the FSS diagnoses are non-existent, making the categorization difficult; there is currently much debate regarding whether the FSS diagnoses represent separate conditions or one overarching diagnosis. 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%. While FSS diagnoses are relatively common within the general community, they are significantly more common among patients presenting with comorbid

psychopathology Psychopathology is the study of abnormal cognition, behaviour, and experiences which differs according to social norms and rests upon a number of constructs that are deemed to be the social norm at any particular era. Biological psychopathol ...

; approximately one third of patients presenting with an FM diagnosis also meet criteria for

posttraumatic stress disorder Post-traumatic stress disorder (PTSD) is a mental and behavioral disorder that can develop because of exposure to a traumatic event, such as sexual assault, warfare, traffic collisions, child abuse, domestic violence, or other threat ...

(PTSD). Similarly, 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. Aside from the physiological symptoms of FSS such as

sleep disturbances A sleep disorder, or somnipathy, is a medical disorder of an individual's sleep patterns. Some sleep disorders are severe enough to interfere with normal physical, mental, social and emotional functioning. Polysomnography and actigraphy are tests ...

chronic pain Chronic pain is classified as pain that lasts longer than three to six months. In medicine, the distinction between acute and chronic pain is sometimes determined by the amount of time since onset. Two commonly used markers are pain that continue ...

and general fatigue, certain psychological symptoms are also associated with most FSSs, such as

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

, depression and

panic disorder Panic disorder is a mental and behavioral disorder, specifically an anxiety disorder characterized by reoccurring unexpected panic attacks. Panic attacks are sudden periods of intense fear that may include palpitations, sweating, shaking, short ...

Signs and symptoms

Functional somatic syndromes are characterized by ambiguous,

non-specific symptoms Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showin ...

that appear in otherwise-healthy people. Overlap in symptomology exists across diagnoses, including gastrointestinal issues,

pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

, cognitive difficulties, and sleep difficulties. Some have proposed to group symptoms into clusters or into one general functional somatic disorder given the finding of correlations between symptoms and underlying etiologies.

Potential causes

Biological factors

One commonly cited hypothesis in the literature implicates the

hypothalamic–pituitary–adrenal axis The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis) is a complex set of direct influences and feedback interactions among three components: the hypothalamus (a part of the brain located below the thalamus), the pituitary gland (a ...

(HPA axis) and

cortisol Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone. It is produced in many animals, mainly by the '' zona fasciculata'' of the adrenal cortex in the adrenal g ...

secretion in the manifestation of somatic symptoms following trauma. The HPA axis plays a major role in moderating the body's

stress response The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...

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. 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 Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...

, 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. For example, fibromyalgia is characterized as a stress response disorder; similar to trauma, patients with fibromyalgia demonstrate a susceptibility to neuroendocrine dysfunctions. Fibromyalgia patients statistically exhibit atypical patterns of daily cortisol secretion, as well as significantly low urine cortisol levels.

Psychological factors

Patients with somatic syndromes such as fibromyalgia and irritable bowel syndrome have significantly higher rates of both physical and

sexual abuse Sexual abuse or sex abuse, also referred to as molestation, is abusive sexual behavior by one person upon another. It is often perpetrated using force or by taking advantage of another. Molestation often refers to an instance of sexual assa ...

prior to the onset of their physiological symptoms, as well as higher rates of previous

emotional abuse Emotions are mental states brought on by neurophysiological changes, variously associated with thoughts, feelings, behavioral responses, and a degree of pleasure or displeasure. There is currently no scientific consensus on a definition ...

, emotional neglect, and physical neglect compared to the general population. Further, childhood trauma such as sexual abuse or

maltreatment Abuse is the improper usage or treatment of a thing, often to unfairly or improperly gain benefit. Abuse can come in many forms, such as: physical or verbal maltreatment, injury, assault, violation, rape, unjust practices, crimes, or other t ...

can indicate an increased propensity for later somatic syndrome onset. Current theories propose an "

attentional bias Attentional bias refers to how a person's perception is affected by selective factors in their attention. Attentional biases may explain an individual's failure to consider alternative possibilities when occupied with an existing train of thought. ...

" as the psychological mechanism by which trauma and somatic symptoms are tied. 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

, and other common somatic symptoms. 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. 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. 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

, 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.

Diagnosis

Diagnosis of a FSS is usually conducted in a "rule-out" method, where physicians rule out other rheumatology disorders with existing biomarkers prior to arriving at a FSS diagnosis.

Treatment

Due to the underlying psychological component of functional somatic syndromes, therapeutic approaches such as

cognitive behavioral therapy Cognitive behavioral therapy (CBT) is a psycho-social intervention that aims to reduce symptoms of various mental health conditions, primarily depression and anxiety disorders. CBT focuses on challenging and changing cognitive distortions (suc ...

(CBT) are common treatments. Multiple

antidepressant Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common Side effect, side-effects of antidepressants include Xerostomia, dry mouth, weig ...

s have also shown to be effective for FSS diagnoses that include chronic pain.

References

{{Reflist Rheumatology