I found this article online:
Every person has a network of pain receptors called cannabinoid receptors, which are part of the overall endocannabinoid system. The majority of these receptors are located in the central nervous system, which includes the brain.
Cannabis, also referred to as marijuana, naturally contains substances called cannabinoids. When a person uses cannabis, the cannabinoids enter the body and attach to your cannabinoid receptors and alter their effect.
For a person with a migraine, researchers say this helps to alleviate pain from the migraine.
Previous research also shows cannabinoids can help alleviate nausea — a common secondary symptom of migraine — by affecting certain endocannabinoid system receptors.
