What causes headaches?
According to the National Headache Foundation, 78% of all headaches are classified as tension headaches, which can be brought on by chronic muscle tension as well as stress, anxiety, or injury. Tension headaches typically feel dull and aching, as if a band is tightening around your head.
The second most common type of headache is migraine, which causes severe pain and often occurs along with vision changes or nausea. Migraine headaches can be hereditary; two genes have been identified that are present in about half of migraine sufferers.
It’s believed that migraine headaches are brought on when the trigeminal nerve, the largest of the cranial nerves, releases irritating chemicals that cause blood vessels on the surface of the brain to swell. Migraine pain is often felt in the eyes or temples. Migraine headaches can be triggered by many controllable factors like lack of sleep, certain foods, missing a meal, stress, caffeine withdrawal, alcohol, and medications.
After tension and migraine, there’s a seemingly never-ending list of other causes of headaches: sinus pressure, viral infection, premenstrual symptoms, stroke, high blood pressure, dehydration, caffeine withdrawal, alcohol consumption, allergies, celiac disease, heavy metal poisoning, carbon monoxide poisoning, and brain conditions such as infection, tumor, and aneurysm.
In addition, medication-overuse or “rebound” headaches can occur when people take pain medication more than three times per week. Yes, that’s right—the exact medication that’s supposed to relieve your headaches can actually cause them.
There are no pain receptors in brain tissue itself, so headache pain is felt in areas surrounding the brain: the head and neck muscles, blood vessels, eyes, ears, sinuses, and the membrane lining the outer surface of the skull. And as you’ll learn in the next section, this is why tight muscles can cause tension headaches: by creating a great deal of pressure in the head.