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The exact mechanism that causes headaches is complex, and research on headache causes remains ongoing. Headache disorders are one of the most common brain-related conditions that people experience. Nearly 50% of adults experience at least one headache per year.
Scientists generally believe a combination of neurological (brain-related), genetic, and environmental factors can lead to the onset of symptoms. Knowing what’s causing your headaches—whether it’s biological or environmental—can help you and a healthcare provider learn how to treat your condition and reduce symptoms.
Theories
There are two categories of headache: primary and secondary. Primary headaches are caused by genetics or have no underlying cause. Secondary headaches are caused by another condition that’s the primary issue that needs to be treated.
Researchers have developed theories for different types of headaches, including migraine, tension, and cluster headaches. These theories are based on how brain function or dysfunction could contribute to symptoms.
Migraine
Migraine is a severe type of headache that usually occurs on one side of the head. It may occur with symptoms like:3
Aura, or visual changes like blind spots, blurry vision, and tunnel vision
Dizziness
Nausea of vomiting
Numbness or tingling
Sensitivity to light or sound
Trouble concentrating
Weakness
Yawning
Migraine has an extremely complex pathophysiology, or the process by which it occurs. This includes cGRP, a molecule that’s released during a migraine attack and involved in cortical spreading depression (CSD). CSD is a wave of brain activity that slowly occurs.
Some evidence suggests that the trigeminal nerve plays a role in the development of migraines. The trigeminal nerve is a part of the nervous system that sends pain and temperature signals from your face to your brain. This nerve releases proteins that cause inflammation when your brain receives a pain signal from it.
Nerve cells become more sensitive to pain as inflammation grows, a process known as sensitization. This process can make it easier for outside stimuli (e.g., lights or noise) to worsen the pain and extend the length of your migraine attack.
Research has shown that an issue with serotonin, a mood-related hormone, may also activate the trigeminal nerve. Why exactly a pain signal activates is still unclear.4
Tension Headaches
Tension headaches are the most common type of headache. Pain may be described as:5
A tight band around the head
All over
Dull
Pressure like
Worse in the back of the neck, scalp, shoulders, or temples
Research on the exact cause remains ongoing. Some evidence suggests that a mechanism in the brain causes the scalp, neck, and shoulder muscles to contract. This causes tension, stiffness, and pain in these body parts.5
Research has shown that the myofascial tissue, or the tissue that covers your facial muscles, can also play a role. The nervous system sends pain signals to the brain if the pain receptors on the myofascial tissue activate. This process might lead to sensitization during a headache episode.6
Cluster Headache
Cluster headaches cause pain that:7
Affects one side of the face, spreading from the temple to the neck and involving the eye
Is burning, sharp, stabbing, or steady
Worsens in five to 10 minutes and lasts 30 minutes to two hours
There are a few theories about the potential cause of cluster headaches. Some evidence suggests that an issue with the function of the hypothalamus could cause cluster headache symptoms. The hypothalamus is a part of the brain that regulates sleep, body temperature, and hormones.8
Another theory offers the idea that the release of histamine may produce accompanying symptoms. Histamine is a chemical the immune system releases in response to allergens and injuries. This theory might explain symptoms like eye redness and a stuffy nose that come with cluster headaches.9