Epidemiology of pain and relation to psychiatric disorders.

Chronic pain is a common pain condition. Some psychiatric disorders, such as anxiety and depression, are also common in the general population. Epidemiological studies found that some psychiatric disorders are more commonly found among persons with chronic pain (e.g., headache, back pain) than those without chronic pain. Why those psychiatric disorders co-occur with chronic pain, however, is not well understood. Further, studies demonstrated that some psychiatric disorders, such as depression, increase the risk of chronic pain as well as its persistence. It is also recognized that chronic pain has a negative impact on the persistence of psychiatric disorders. The observations from clinical studies suggest that chronic pain is not a common comorbidity among individuals with other psychiatric disorders, such as dementia and schizophrenia. It is not clear if this is a consequence of any specific biological mechanism, or methodology problems in the studies. This paper provides an overview on the distribution of chronic pain and psychiatric disorders, followed by a review of studies that have demonstrated the association between psychiatric disorders and chronic pain.