[Comorbidity of chronic pain and fatigue : Common mechanisms, common treatment steps?]

Fatigue and chronic pain show a high level of comorbidity and are both not only frequent symptoms of chronic diseases without known somatic structural causes (e.g. irritable bowel syndrome or nonspecific low back pain) but also as leading symptoms of diseases with a specific etiology (e.g., cancer, rheumatoid arthritis or multiple sclerosis). Fatigue and pain also often co-occur for months or years after overcoming an acute organic illness, such as an acute bacterial or viral infection. In all cases, fatigue and pain can be accompanied by increased anxiety or depression. Moreover, research indicates that psychosocial factors, such as emotional distress, dysfunctional behavioral responses to fatigue or pain or social stigmatizing, can be involved in the perpetuation of the complaints and also independent of the etiology of the underlying disease. Physiological processes, such as autonomic dysregulation, an altered activation of adrenocortical activity as well as altered brain activity are increasingly being discussed as biological mechanisms. These common factors suggest a transdiagnostic approach investigating overlapping features in terms of biopsychosocial mechanisms that may play a role not only in the maintenance of pain but also of fatigue. As a consequence, both the diagnostics and management can be provided in a more individualized and resource-efficient way. The present narrative review gives a preliminary summary of the transdiagnostic mechanisms and possible clinical approaches for fatigue and chronic pain.