What Causes Headaches?

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:

• 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.

Tension Headaches 

Tension headaches are the most common type of headache. Pain may be described as:

• 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.

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.

Cluster Headache

Cluster headaches cause pain that:

• 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.

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.  

Secondary Headaches

Secondary headaches occur as a result of another health condition. These include:

• Blood vessel problems
• Conditions that affect the brain
• Head trauma
• Hydrocephalus (build-up of fluid in the cavities of the brain)
• Infections of the head and neck (e.g., pharyngitis, sinusitis, and meningitis) 
• Severe hypertension (high blood pressure)
• Subdural hematoma (blood that gathers on the brain's surface)
• Tumor

Are Headaches Hereditary?

People with close family members who have migraine, tension, and cluster headaches are more likely to develop the condition themselves. Having one or more parents with a headache disorder gives you more than a 50% chance that you will develop headaches. 

Research on the exact genetics of headaches is ongoing. You have to inherit one or more genetic mutations that make you more vulnerable to headaches for the condition to be passed down. Genetic mutations alone don't automatically mean you will have headaches. Environmental factors (e.g., stress) also need to be present for you to experience headaches. 

Research has identified 38 genetic mutations that can make you more prone to headaches. Experts may be able to find treatments that target these genetic mutations and ultimately help reduce symptoms. 

Who Gets Headaches?

Some people may be more likely to develop headaches than others. These demographic factors include: 

• Age: People between the ages of 20–40 are most likely to experience headaches.
• Sex: Women are three times more likely to develop a headache disorder than men.
  

Risk Factors

Every person with headaches experiences them differently. Certain environmental risk factors may raise your risk of headaches or trigger an episode if you already have a headache disorder. 

Risk factors include:     

• Drinking alcohol
• Exposure to bright lights 
• Eye strain
• Lack of sleep or general fatigue
• Missing meals
• Overuse of caffeine 
• Physical overexertion
• Smoking
• Spending too much time on screens
• Stress
  

A Quick Review

The exact cause of primary headache disorders is ongoing. Experts have theorized that a combination of neurological, genetic, and environmental risk factors can lead to the onset of symptoms.

It's not always possible to avoid a headache. You may see a healthcare provider for testing and treatment options if you notice symptoms or a change in your existing symptoms.