Clinical Enocannabinoid Deficiency is a condition in which the body has a lack of production or overproduction of endogenous cannabinoids. The term was coined by Dr. Ethan Russo in 2004 through his conductive study Clinical Endocannabinoid Deficiency Reconsidered: Current Research Supports the Theory in Migraine, Fibromyalgia, Irritable Bowel, and Other Treatment-Resistant Syndromes and was revisited again in 2012. In his research he discovered the treatment conditions such as migraines, fibromyalgia, Irritable Bowel Syndrome and other previously believed to be treatment resistant conditions may be treated using cannabinoid therapy without any adverse side effects.  This condition can exist in all mammals but has only been primarily found to be in the human species. Endocannabinoids role is to regulate homeostasis within the body via the endocannabinoid system. 
The endocannabinoids produced are anandamide (AEA) that manages the central nervous system via the CB1 receptor and arachidonoylglycerol (2-AG) manages the peripheral nervous system via the CB2 receptor. A deficiency is caused when the body begins to cease production or begin to overproduce one or more of these endocannabinoids, thus causing an imbalance within the system resulting in conditions that have been deemed “treatment resistant” because until recently we haven't fully understand the root cause.