Why Do We Get Headaches?

Your brain has 86 billion neurons and zero pain receptors, so why does a headache feel like it's happening inside your skull? It's one of the strangest facts in human biology, and it changes how you think about every headache you've ever had. In this episode, Jen, Chris, and Matt unpack where head pain actually comes from, why migraines arrive with nausea and light sensitivity, why caffeine both helps and hurts, and why reaching for painkillers too often can quietly make things worse. With over 200 classified types of headache and more than 400 potential migraine triggers, generic advice rarely works. Understanding the mechanism does. By the end, you'll see headaches not as random bad luck but as signals worth paying attention to. In this episode: (00:00) Can your brain feel pain? (01:50) How common headaches really are (03:34) Where head pain actually comes from (05:13) Serotonin, CGRP, and hormones (07:51) Tension, migraine, and cluster headaches (10:07) Triggers, caffeine, and medication overuse (12:34) What actually helps, and when to see a doctor Where Headache Pain Really Comes From (00:03:34) The brain itself can't feel pain, but the structures around it can. The blood vessels, the meninges (the membranes around the brain), and the muscles of the scalp, face, and neck are full of pain receptors called nociceptors. These all feed into the trigeminal nerve, the head's main communication hub, which carries the signal up to the brainstem to be felt as pain. "So the brain isn't actually feeling the pain, it's more like it's being told about the pain from somewhere else." — Matt Because the brainstem also links to systems handling balance, digestion, and light and sound, a bad headache often brings nausea, dizziness, and the urge to shut everything out. That instinct to lie down in a dark room is your nervous system asking for less input. The Chemicals That Turn Headaches Up and Down (00:05:13) A few key chemicals control how loud the pain signal gets: Serotonin affects blood vessels as well as mood. When levels drop, vessels can expand and amplify pain. CGRP (calcitonin gene-related peptide) is released during migraine attacks and dilates blood vessels. It's so central that a whole class of modern migraine drugs is designed to block it. Oestrogen drops before menstruation can trigger migraines, one reason migraines are around three times more common in women than men. In migraine specifically, a process called cortical spreading depression sends a slow wave of altered electrical activity across the brain. It's visible on brain imaging, and it's likely what causes auras. A migraine is a real, measurable biological event, not "just a headache." Tension, Migraine, and Cluster Headaches Explained (00:07:51) The three main types differ in location, severity, duration, and the symptoms they bring: Tension headaches are the most common, affecting around 80% of adults at least once a year (roughly two billion people). They feel like a tight band, are usually mild to moderate, and rarely bring nausea or light sensitivity. Migraines are a neurological condition affecting around 12% of adults. The pain is throbbing and often one-sided, commonly with nausea, light and sound sensitivity, and sometimes aura. They can last from four to 72 hours. Cluster headaches affect about 0.1% of people but are among the most intense pain in medicine. They come in cycles and focus around one eye. Caffeine, Painkillers, and What Actually Helps (00:10:07) Caffeine confuses everyone because it works both ways. Small amounts can help by constricting blood vessels and boosting painkillers, but 400mg or more a day was linked with over a 40% higher prevalence of headache or migraine. Withdrawal can trigger one too. The surprising one is medication overuse. Taking painkillers on more than 10 to 15 days a month can flip the system so the medication itself maintains the headache. The encouraging part is that breaking the cycle often brings real improvement (worth a GP conversation rather than stopping everything overnight). What helps most is reassuringly simple: regular sleep with a fixed wake-up time, steady hydration, regular meals, and stress management. One trial found that drinking about 1.5 litres more water a day improved headaches in almost half of participants. "Headaches are almost a bit like a pressure gauge for everything else going on inside your body." — Jen About So That's Why So That's Why is a weekly podcast where Jen, Chris, and Matt unpack the science behind everyday health questions. No jargon, no judgment, just genuine curiosity and proper research.