The natural occurring cannabinoid, anandamide, is very similar to THC. But when there is a deficiency of anandamide, it causes migraines. In a study to find out of a deficiency or imbalance in the endocannabinoid system was the cause of migraines, they found that a real deficiency of anandamide caused an imbalance that resulted in migraines. During the study, it was discovered that CBD can correct this imbalance.