You make a great point about caffeine both causing and relieving headaches, but it’s important to note that its effect can vary. Caffeine constricts blood vessels, which helps relieve headaches, especially for migraines, which is why it's in many pain medications. However, for regular caffeine drinkers, it can also trigger headaches if consumed in excess. The withdrawal headaches are caused by blood vessels expanding as the body adjusts to the lack of caffeine. The relationship between caffeine and headaches is different for everyone; some people find relief from small amounts, while others may get headaches from it. It would be helpful to explore how much caffeine is too much, especially for people with chronic headaches.