Functional somatic syndrome

Functional somatic syndrome
Functional somatic syndrome
Specialty	Psychiatry, psychosomatic medicine, psychoneuroendocrinoimmunology
Differential diagnosis	Organic/medical illness, primary psychiatric disorders (depression/anxiety with somatic features; psychotic disorders with somatic delusions), functional neurological disorder, somatic symptom disorder, mass psychogenic illness, illness anxiety disorder, Munchausen's and Munchausen's by proxy, deconditioning, malingering
Treatment	Psychological therapies Cognitive-behavioural therapy; Psychodynamic Psychotherapy; Psychoeducation; relaxation therapy; ; Physical therapies Exercise (sports); Supervised aerobic training; Behavioral activation therapy; ; Other non-pharmacological interventions;
Medication	Primarily non-pharmacological treatments SSRIs; SNRIs; Tricyclic Antidepressants; Gabapentinoids (Pregabalin, Gabapentin); Low-dose Antipsychotics; ;

Functional somatic syndrome (FSS) (sometimes termed "non-specific physical disorders") refers to a cluster of chronic conditions, characterized by persistent physical symptoms without demonstrable structural or organic disease despite extensive medical testing.

Contemporary theories describe the aetiology as involing a dysregulation in the brain-body signaling, which includes negative emotional states pathologically activating somatosensory and nociceptive circuits, generating genuine physical sensations through central sensitization, maladaptive stress response systems and learned neuroplastic rewiring, with symptoms resulting from complex interactions between the autonomic nervous system, hypothalamo-pituitary axis and possibly the immune system, rather than from peripheral tissue damage.

Fibromyalgia, chronic fatigue syndrome (now called ME/CFS) and irritable bowel syndrome are some of the most common disorders that have been described as FSS conditions, although the classification of ME/CFS as an FSS has been increasingly called into question in the recent years. Functional somatic syndromes are very common, although specific criteria differ, they are estimated to affect about anywhere from 4% to 16% of the general population.