Observed in 50 to 90% of the patients, sleep disorders are an important element of chronic pain syndromes. In addition to the depression which is often an associated factor, the severity of the insomnia element is directly related to the severity of the pain. In a healthy subject, sleep deprivation leads topain and EEG changes identical to those observed in patients with chronic pain. Studying ... [Show full abstract] the daily activity pattern in these patients reveals that sleep disorders can be a favoring factor for pain. Work is beginning to appear on the therapeutic implications.