Cluster headaches are a fairly common form of chronic, recurrent headache. Unlike migraines, they affect men more often than women. They can affect people of any age but are most common between adolescence and middle age. There does not seem to be a pattern among families in the development of cluster headaches.

Cluster headaches occur as a severe, sudden headache. No specific cause has been found for the disorder, but it appears to be related to a sudden release of histamine and/or serotonin by body tissues.

The onset is sudden, and it occurs most commonly during the dreaming (REM) phase of sleep. Cluster headaches may occur daily for months, alternating with periods without headaches (episodic), or they can occur for a year or more without stopping (chronic). A person may experience alternating chronic and episodic phases.

Some people who experience cluster headaches are heavy smokers. Alcohol use may trigger attacks. Glare, stress, or certain foods may trigger an attack.