Causes and Risk Factors of Headaches

The cause of headaches, or why headaches develop, is complex, often involving an intricate web of pain receptors, abnormal brain processes, genetics, and a neurological phenomenon called sensitization. Outside or environmental factors are also commonly involved, serving as headache triggers—the factors that unmindfully activate pain signals within the brain.

By understanding the biology behind your headaches (at least what experts know so far), you can hopefully tease out what parts of your head pain you can perhaps control (like various environmental triggers), and which ones you cannot (like your genetic makeup).

Common Causes

Headaches are unpleasant experiences, so treating them promptly is key. But in order to effectively treat your headaches, you must understand them.

The vast majority of headaches fall into three categories:

• Migraine
• Tension-type headache
• Cluster headache

These three headache types are primary headache disorders, meaning they exist on their own and are not due to some other condition (called secondary headaches).

Migraine

Migraine may be the most complicated headache disorder and feels like a moderate to severe throbbing sensation on one or both sides of the head. Nausea, vomiting, sensitivity to light (photophobia), and/or sound (phonophobia) commonly co-occur with a migraine headache.

Once the trigeminal nerve fibers are activated, they release various peptides, like calcitonin gene-related peptide (CGRP) and substance P. These peptides induce a phenomenon called neurogenic inflammation, which is connected to the prolongation and intensification of pain in migraine.

Eventually, neurogenic inflammation may lead to a process called sensitization, whereby your nerve cells become more and more responsive to stimulation.

Other variables linked to migraine development include structural brain changes and serotonin release. Lastly, a phenomenon called cortical spreading depression—where waves of electrical activity spread across the brain—is believed to be the culprit behind migraine aura.

Tension-Type Headache

Tension-type headache is the most common headache type and is often described as a squeezing or tight sensation around the head. Along with this pressure or "rubberband-around-the-head" sensation, tension-type headaches may be associated with muscle tenderness in the muscles of the head, neck, or shoulders.

Experts believe that tension-type headaches result from the activation of myofascial (the tissue that covers muscles) pain receptors. Once activated, pain signals are transmitted to the brain.

As with migraines, experts also believe that the sensitization of pain pathways in the brain occur with tension-type headaches. This sensitization is thought to play a pivotal role in the transformation from episodic to chronic tension-type headache.

Cluster Headache

Cluster headaches are uncommon and often begin without warning. These headache attacks are often short-lived, lasting between 15 and 180 minutes, and they are excruciating—causing a burning, piercing, or stabbing pain located in or around the eye or temple.

The pathogenesis, or the "why" behind cluster headache development, is not fully understood. Experts suspect that the cause is likely linked to the hypothalamus—a gland located within your brain that helps regulate sleep and circadian rhythm.

In addition to the hypothalamus, trigeminal nerve stimulation, histamine release, genetics, and activation of the autonomic nervous system may contribute to the development of cluster headaches.

Injury or Illness (Secondary Headaches)

Head injuries or trauma or an acute illness, ranging from a run-of-the-mill viral or sinus infection to more serious infections, like meningitis, may cause headaches.

In addition, serious underlying (non-infectious) health conditions may cause headaches.

Examples include:

• Brain tumor
• Brain bleed (subarachnoid hemorrhage and cerebral hematoma)
• Ischemic Stroke
• Vascular or autoimmune process, like giant cell arteritis
• Pituitary Apoplexy
• Acute Hypertensive Crisis

Genetics

Headaches, especially migraine headaches, tend to run in families. In fact, according to the American Migraine Foundation, if one or both of your parents suffer from migraine, there is a 50% to 75% chance that you will too.

Genetics Behind Migraines

That said, the genetic basis for migraines is complicated. For most migraine types, in order for a person to develop migraines, they must have inherited one or more genetic mutations.

But having a certain genetic mutation(s) is not necessarily a slam dunk case for developing migraines. Rather, that genetic mutation may make you more vulnerable to getting migraines, but other environmental factors, like stress, hormone changes, etc, need to be present for the migraine disorder to manifest.

The good news is that researchers are working tirelessly to identify genetic mutations that increase migraine risk. So far, 38 single nucleotide gene mutations have been discovered, although how these discovered mutations can translate into migraine therapies remains unclear.

Familial Hemiplegic Migraine

When linking migraines and genes, it's important to mention a rare but severe type of migraine called familial hemiplegic migraine. With this migraine type, a person experiences temporary weakness on one side of their body during the aura phase.

Mutations in four specific genes have been linked to familial hemiplegic migraine. These four genes include:

• CACNA1A gene
• ATP1A2 gene
• SCN1A gene
• PRRT2 gene

Other Primary Headache Disorders

In addition to migraines, keep in mind genetics likely plays a role (albeit more minor) in the pathogenesis of cluster headaches and tension-type headaches. Overall, the research into these specific genetic patterns is less robust than with migraines.

Lifestyle and Environment

Numerous lifestyle-related and environmental factors have been found to trigger primary headache disorders, especially migraines. It's believed that these triggers are the factors that signal the brain, nerve, muscle, and/or blood vessels to go through changes that ultimately create head pain.

Common Migraine Triggers

Some common triggers for migraines include:

• Stress
• Hormone fluctuations, like that seen just prior to menstruation (called menstrual migraine)
• Weather changes
• Certain foods or beverages (e.g., nitrates, alcohol, caffeine, aspartame, to name a few)
• Sleep disturbances
• Odors
• Skipping meals

Common Cluster Headache Triggers

The two most common triggers are:

• Cigarette smoking
• Alcohol

Common Tension-Type Headache Triggers

Some common triggers for tension-type headaches (of which there is a large overlap with migraines) include:

• Stress
• Intense emotions
• Abnormal neck movement/position
• Lack of sleep and fatigue
• Fasting or not eating on time
• Noise

Trigger Factors for Other Types of Headaches

Various lifestyle and environmental factors have been linked to other types of headaches. For example, missing your morning coffee can precipitate a caffeine withdrawal headache, which is located on both sides of the head, worsens with physical activity, and can be quite painful.

Another common type of headache is medication overuse headache, also called "rebound headache." This headache occurs after frequent and excessive use of a headache or migraine medication—for example, a triptan or a nonsteroidal anti-inflammatory (NSAID).

Some daily activities like strenuous exercise, sex, or coughing can trigger headaches; although these primary headache disorders are uncommon and warrant investigation by a headache specialist.

Lastly, while alcohol can trigger a person's underlying primary headache disorder, it can also cause its own headache, either as a cocktail headache or as a hangover headache. A hangover headache is throbbing, like a migraine, but is usually located on both sides of the forehead and/or temples, like a tension-type headache.

In the end, remain dedicated and empowered in your journey to learning more about headaches—but also, be good to yourself and seek out guidance from your primary care physician or headache specialist.