Tension headaches are caused by a combination of heightened sensitivity in the muscles and nerves around your skull, amplified by everyday triggers like stress, poor posture, lack of sleep, and dehydration. They’re the most common type of headache, affecting up to 70% of some populations and striking women about 50% more often than men. Unlike migraines, tension headaches don’t have a single clear biological origin, which is why researchers now view them as the result of multiple overlapping factors rather than one root cause.
How the Pain Actually Works
The traditional explanation, that tense muscles cause the pain, is only part of the story. Tension headaches involve changes in how your nervous system processes pain signals from the muscles of your head, neck, and shoulders. Normally, pain signals travel through specific nerve fibers reserved for detecting harmful stimuli. But in people with tension headaches, sustained input from these muscles causes even nerve fibers that usually carry harmless signals (like light touch or pressure) to start transmitting pain. This is called peripheral sensitization, and it explains why the muscles around your skull can feel tender or sore even between headache episodes.
Trigger points in the muscles at the base of your skull and along your neck play a significant role. When activated, these tight, irritable knots in muscle tissue produce referred pain that spreads across one or both sides of the head, mimicking the classic band-like pressure people describe. Studies confirm that activating trigger points in the head and neck muscles reliably reproduces the pain patterns of tension headaches.
Nitric oxide, a signaling molecule your body produces naturally, also appears to be involved. In one controlled trial, when researchers infused a nitric oxide-releasing compound into people with chronic tension headaches and healthy volunteers, those with headaches developed significantly more pain, including a delayed headache peaking around eight hours later. Nitric oxide seems to amplify pain signaling and promote sensitization in the brain’s pain-processing pathways.
Why Episodic Headaches Become Chronic
Most tension headaches are episodic, lasting anywhere from 30 minutes to 7 days and occurring fewer than 15 days per month. But for some people, they become chronic, occurring 15 or more days monthly. The shift happens when repeated pain signals physically change how your brain and spinal cord handle incoming information. Over time, the central nervous system begins amplifying pain signals while simultaneously losing its ability to dampen them. This process, central sensitization, means your pain threshold drops. Stimuli that wouldn’t normally hurt, like normal pressure on your scalp or neck, start registering as painful.
Pain medication itself can accelerate this transition. Using simple painkillers on 15 or more days per month, or combination analgesics and stronger medications on 10 or more days per month for three months or longer, can cause medication overuse headache. The very drugs meant to relieve headaches begin perpetuating them, trapping people in a cycle of daily or near-daily pain.
Stress and Cortisol
Stress is the most commonly reported trigger, and the connection is physiological, not just psychological. When you’re stressed, your brain kicks off a hormonal chain reaction: the hypothalamus signals the pituitary gland, which signals the adrenal glands to release cortisol. In short bursts, this is useful. But repeated or prolonged stress keeps this system activated, promoting inflammation in pain pathways and sensitizing the nerves that detect pain in your head and neck. This “hyperalgesic priming” essentially lowers the bar for what triggers a headache, so smaller stressors or minor muscle tension that you’d normally shrug off can set one off.
The relationship works in both directions. Chronic headaches are themselves a source of stress, which keeps cortisol elevated and maintains the sensitization that makes more headaches likely.
Posture and Screen Time
Forward head posture, the position your head drifts into during long stretches of computer or smartphone use, is a well-documented contributor. When your head juts forward, the small muscles at the base of your skull (the suboccipital muscles) have to work dramatically harder to hold it up. Research measuring electrical activity in these muscles found that their workload nearly doubles in a forward head position, jumping from roughly 10-18% of their maximum capacity in a neutral position to 34-42% when the head is pushed forward.
That sustained overload does several things. It strains the posterior cervical spine and soft tissues, disrupts the normal length-tension relationship in your neck muscles, limits head and neck mobility, and activates trigger points in the suboccipital muscles. Those activated trigger points then refer pain upward across the back and sides of the head. If your headaches tend to start at the base of your skull and creep upward after hours at a desk, this mechanism is likely involved.
Sleep, Dehydration, and Other Triggers
Poor sleep independently lowers your pain threshold. People with tension headaches who also have disturbed sleep show measurably lower tolerance for pressure on their head and neck muscles. Researchers believe that insufficient sleep enhances central sensitization on its own, separate from mood issues like depression (which also lowers pain thresholds independently). This means that even if you’re not particularly stressed, a few nights of bad sleep can prime you for a headache.
Dehydration contributes through a surprisingly direct mechanism: when your body loses fluid, brain tissue contracts slightly and pulls away from the skull. This tugging activates pain-sensitive nerves surrounding the brain, producing a headache that typically resolves once you rehydrate.
Other common triggers include skipped meals, caffeine withdrawal, eye strain, jaw clenching, and alcohol. Most people with frequent tension headaches can identify two or three personal triggers that reliably set off an episode.
How Tension Headaches Differ From Migraines
Tension headaches produce a pressing or tightening sensation on both sides of the head, often described as a band squeezing around the forehead. The pain is mild to moderate. Migraines, by contrast, are typically one-sided, pulsating, and moderate to severe.
The practical differences matter most when deciding what you’re dealing with:
- Physical activity: Walking or climbing stairs makes migraines worse but does not worsen tension headaches.
- Nausea and vomiting: Common with migraines, essentially absent with episodic tension headaches (though mild nausea can occur in chronic cases).
- Light and sound sensitivity: Present in over 80% of migraine episodes but uncommon with tension headaches. At most, you might experience sensitivity to light or sound, but not both simultaneously.
If your headaches regularly come with nausea, throbbing pain on one side, or force you to lie down in a dark room, you’re more likely dealing with migraines than tension headaches, even if they feel like pressure. The two conditions can also coexist, making it harder to sort out which is which without tracking your symptoms over time.