Conditions InDepth: Headache
Headache refers to head pain (cephalgia). There are several different types of headache, including:
Headaches may also have other causes, such as:
- Side effects of medicines
- Overusing medicines to treat headaches
- Head injury
- Increased pressure in the head
While the precise cause of many headaches remains unknown, several theories exist. The causes of a headache vary depending on the type of headache.
refers to head pain associated with stress and muscle contraction. These headaches may occur only occasionally in response to a stressful event. They may also be chronic, occurring frequently. Some tension headaches are nearly constant, with daily pain that may vary in intensity. Tension headaches occur when muscles in the neck, face, and scalp contract and produce pain. The precise cause of this muscle contraction is unknown, but stress,
, eyestrain, and other factors may contribute.
is a type of recurring headache that involves blood vessels, nerves, and brain chemicals. Sensations such as visual changes, called auras, may precede a migraine. The International Headache Society has a system that classifies migraines as one of two types: migraine occurring with an aura (formerly called “classic”) and migraine occurring without an aura (formerly called “common").
Migraines may occur several times a week or once every couple of years. Migraines may be so severe that they interfere with your ability to work and carry on normal activities.
An internal or external trigger sets off a process that results in migraine headaches. The exact trigger is often unknown. It is possible that the nervous system reacts to the trigger by conducting electrical activity that spreads across the brain. It leads to the release of brain chemicals, which help regulate pain.
is a type of severe, recurring pain that is located on one side of the head. It received its name from the clustering or pattern of frequent headaches that usually occur.
There are two main types of cluster headaches. Either type of headache may convert to the other type:
- Episodic cluster headaches—(80% of all cases) occur one or more times daily for several months. The headaches then enter a period of remission and come back months or years later.
- Chronic cluster headaches—(20% of all cases) occur almost daily with, at most, one headache-free month during a year.
The cause of cluster headaches is unknown.
Headache—frequently asked questions. National Headache Foundation website. Available at:
. Accessed November 7, 2012.
NINDS headache information page. National Institute of Neurological Disorders and Stroke
website. Available at:
. Updated September 2012. Accessed November 7, 2012.
International classification of headache disorders. 2nd ed.
International classification of headache disorders. 2nd ed. (1st revision.)