What is clinical endocannabinoid deficiency syndrome?

Clinical endocannabinoid deficiency (CED) is a theoretical condition proposed by Dr. Ethan Russo in 2004, suggesting that deficient endocannabinoid tone may underlie conditions including migraine, fibromyalgia, and irritable bowel syndrome. The hypothesis is based on: (1) the ECS regulates pain, gut motility, and mood — all affected in these conditions; (2) patients with migraine have lower CSF anandamide levels than controls; (3) these conditions share features of central sensitization and respond to treatments that enhance endocannabinoid tone. CED remains a hypothesis rather than a confirmed diagnosis — there is no validated biomarker, diagnostic test, or clinical criteria. It has not been formally recognized by any medical organization. However, it has generated research interest and provides a theoretical framework for why cannabis may help these conditions. Critics note it risks circular reasoning.