People get different types of headaches, prompted by all sorts of diverse causes and triggers.
The woman who sits at the computer all day, clicking away at a keyboard, for instance: She might get an eyestrain headache from reading the small print on her screen, or she may feel a tension headache due to craning her neck forward.
Someone else's headaches may be a symptom of anxiety. While it may cause anxiety to not know why a headache strikes, sometimes the cause is unknown or complex, as with migraine headaches.
When it comes to headache triggers, caffeine is problematic, no matter how you brew it, chug it, or eat in a chocolate bar. If you're addicted to caffeine and you don't get your usual dose, you may have to endure a withdrawal headache or two. On the other hand, caffeine itself may trigger a headache.