By definition, chronic daily headaches occur 15 days or more a month, for longer than three months. True (primary) chronic daily headaches aren't caused by another condition.

There are short-lasting and long-lasting chronic daily headaches. Long-lasting headaches last more than four hours. They include:

• Chronic migraine
• Chronic tension-type headache
• New daily persistent headache
• Hemicrania continua

Chronic migraine

This type typically occurs in people with a history of episodic migraines. Chronic migraines tend to:

• Affect one side or both sides of your head
• Have a pulsating, throbbing sensation
• Cause moderate to severe pain

And they cause at least one of the following:

• Nausea, vomiting or both
• Sensitivity to light and sound

Chronic tension-type headache

These headaches tend to:

• Affect both sides of your head
• Cause mild to moderate pain
• Cause pain that feels pressing or tightening, but not pulsating

Hemicrania continua

These headaches:

• Affect only one side of your head
• Are daily and continuous with no pain-free periods
• Cause moderate pain with spikes of severe pain
• Respond to the prescription pain reliever indomethacin (Indocin)
• Can become severe with development of migraine-like symptoms

In addition, hemicrania continua headaches are associated with at least one of the following:

• Tearing or redness of the eye on the affected side
• Nasal congestion or runny nose
• Drooping eyelid or pupil narrowing
• Sensation of restlessness

The causes of many chronic daily headaches aren't well-understood. True (primary) chronic daily headaches don't have an identifiable underlying cause.

Conditions that might cause nonprimary chronic daily headaches include:

• Inflammation or other problems with the blood vessels in and around the brain, including stroke
• Infections, such as meningitis
• Intracranial pressure that's either too high or too low
• Brain tumor
• Traumatic brain injury

Medication overuse headache

This type of headache usually develops in people who have an episodic headache disorder, usually migraine or tension type, and take too much pain medication. If you're taking pain medications — even over-the-counter — more than two days a week (or nine days a month), you're at risk of developing rebound headaches.

Factors associated with developing frequent headaches include:

• Female sex
• Anxiety
• Depression
• Sleep disturbances
• Obesity
• Snoring
• Overuse of caffeine
• Overuse of headache medication
• Other chronic pain conditions

If you have chronic daily headaches, you're also more likely to have depression, anxiety, sleep disturbances, and other psychological and physical problems.