What are headaches?

The brain itself doesn’t feel pain. Though the brain has billions of neurons (cells that transmit sensory and other information), it has no pain receptors. The ache from a headache comes from other nerves — inside blood vessels in your head, for example — telling your brain something is wrong.

Who gets headaches?

Headaches are a major public health problem. They are one of the most common sources of pain and suffering. They are also a leading cause of disability, emergency-room visits, and work and school absences.

Globally, according to the World Health Organization:

• Nearly all people have a headache at some time in their lives.
• About half of adults have a headache at least once a year.
• Up to one in 20 adults have a headache every day or nearly every day.
• Migraines affect at least one in seven adults.
• Migraines affect about three times as many women as men.

In the U.S.:

• Headaches are among the top five reasons Americans go to an emergency room, according to a 2018 analysis of federal data*. For women under 64, it’s the third-leading cause.
• One in six adults (one in five women) reported a migraine or severe headache in the prior three months, according to 2017 national health statistics.
• Among those ages 18 to 64, one-third had a migraine or severe headache in the prior three months.

Headache categories

Headaches are categorized as either:

• Primary: The headache is the sole medical problem. This type makes up more than 90% of headaches.
• Secondary: The headache is a symptom of another medical issue, anything from a sinus infection to a stroke or tumor.

Headache types

The International Headache Society’s classification system lists more than 200 types and subtypes of headache, but about 90% are tension, migraine or cluster.

Tension

Tension headaches, the most common type, deliver a dull ache to both sides of the head. These headaches are usually treated with over-the-counter medication that contains ibuprofen (such as in Advil) or acetaminophen (Tylenol).

Migraine

Migraines affect an estimated 38 million Americans. Women, most often in their 30s, are three times more likely to get migraines. Migraines can be hereditary (passed down from a parent).

Migraine and depression: People who get migraines are about four times more likely to have depression and anxiety. It’s a two-way street, with each increasing the risk for the other.

Migraine with aura: Roughly one-quarter of people with migraines have aura symptoms — sensory changes that signal a migraine is coming. Symptoms may include seeing flashes of light, having a tingling sensation or having trouble speaking.

Dr. Juliette Preston discusses the myths and truths about women and migraines.

Cluster

This type can be extremely painful, with stabbing pain near one eye or on one side of the head. Attacks usually occur in groups (clusters), with as many as eight in one day. Pain-free periods can last weeks, months or years. Cluster headaches are four times more common in men.

Headache causes

Headaches can have many causes, including injury or an underlying illness. But the vast majority are primary headaches, meaning the headache is the only medical issue. For these, the most common causes include:

• Medication overuse (taking more than 10 doses of headache medication a month has been found to cause headaches)
• Drinking alcohol
• Skipping meals
• Eating certain foods
• Dehydration
• Stress and anxiety
• Lack of sleep

Headache triggers: Some causes are referred to as triggers. Some patients track their triggers so they can avoid them and ward off headaches.

Find more information, including answers to frequent questions, on our Headache FAQ and Resources page.

_{* The Prevalence and Impact of Migraine and Severe Headache in the United States: Figures and Trends From Government Health Studies}