Recent nation-wide epidemiological data confirm the well-known clinical observation of a strong relationship between pain syndromes and disordered sleep.

In experimental settings of pain patients as well as healthy subjects, pain perception shows a strong circadian pattern exhibiting significant variation over the 24-hour sleep-wake period. Several lines of scientific evidence indicate that homoeostatic components of sleep may mask circadian pain perception, which results in a two-process model of pain regulation depending on the circadian sleep-wake status.

Since pain may worsen sleep, sleep deprivation increases pain, and quality of sleep not only affects nocturnal pain but influences pain during daytime hours, models of interactive pathomechanisms of pain and sleep are widely accepted.

Clinical consequences include various treatment methods that consider both, pain and sleep. E.g., intake of pain medication should follow circadian aspects which assure sufficient pain reduction at early morning hours; ideal pain medication at night should have hypnotic properties, including the promotion of deep sleep; pain medication during daytime hours should activate patients to support good sleep during the following night. Psychotherapy needs to support both, the management of pain and of sleep.