Eternal, cannabis causes both vasoconstriction (blood vessel tightening) and vasodilation (blood vessel relaxation), most often with the constriction happening in the period right after you smoke and the dilation occurring once the THC and other cannabinoids have kicked in. Both vasoconstriction and vasodilation are headache triggers in lot of people.

People generally have headaches because the vessels in their scalp or the underlying muscle layer go into spasm; because of tension, which also causes muscle spasms and/or tightness; or because of a trigger in the trigeminal nerve pathway that causes chemicals to be released that make the blood vessels in the brain's outer covering become dilated and inflamed. That third one, the trigeminal trigger, is thought to be what happens in migraines. The medicines that best treat migraines nowadays are very powerful vasoconstrictors that cause those dilated, spasming veins to tighten up and behave themselves.

Sorry for the long answer, but we've been learning all about headaches in my neuroscience class. Headaches are the worst! So sorry you're having that experience.
birdgirl73 Reviewed by birdgirl73 on . PERMANENT HEAD ACHES ANYONE? Whenever i go through a big weed phase and im smoking every day i get the worst head aches, like 24/7. my head is constatly hurting, it feels like there is an air bubble trapped in the back of my headsometimes it also feels like my brain is full of pressureor like im wearing a 10 ound hat on my head. think this is just the weed or its neck spazzim or something, or maybe im not getting enough excersize? but it only happens when i start smoking a lot of weed any body have the same thing? Rating: 5