We now know that CBD from hemp and other cannabinoids activate the endocannabinoid system, however these discoveries are only recent!
The first endocannabinoid was discovered in 1992. Anandamide was the first, naturally occurring endogenous cannabinoid, or endocannabinoid. It was found by Raphael Mechoulamas well as NIMH researchers William Devane and Dr. Lumir Hanus.
Anandamide is a molecule which acts as a neurotransmitter, and which has a structure very similar to that of tetrahydrocannabinol, the active constituent of cannabis. It is messenger molecule that plays a role in many bodily activities, including appetite, memory, pain, depression, and fertility - hence its name, which is derived from the word 'ananda' which means 'extreme delight' or 'bliss' in the Sanskrit language.
Endocannabinoids and their receptors are found throughout the human body: in the brain, organs, connective tissues, glands, and immune cells. Not only do humans posses this system, but so do mammals...yes, that means your pets too.
The endocannabinoid system, with its complex actions in our immune system, nervous system, and all of the body's organs, is literally a bridge between body and mind.