Fibromyalgia is classed as a disorder of pain processing due to abnormalities in how pain signals are processed in the central nervous system. The American College of Rheumatology classifies fibromyalgia as being a functional somatic syndrome. The expert committee of the European League Against Rheumatism classifies fibromyalgia as a neurobiological disorder and as a result exclusively give pharmacotherapy their highest level of support. The International Classification of Diseases (ICD-10) lists fibromyalgia as a diagnosable disease under "Diseases of the musculoskeletal system and connective tissue," under the code M79-7, and states that fibromyalgia syndrome should be classified as a functional somatic syndrome rather than a mental disorder. Although mental disorders and some physical disorders commonly are co-morbid with fibromyalgia – especially anxiety, depression, irritable bowel syndrome, and chronic fatigue syndrome – the ICD states that these should be diagnosed separately.