The therapeutic utility of legal marijuana is rooted in its interaction with the human Endocannabinoid System (ECS). The ECS is a complex cell-signaling system that plays a crucial role in regulating a range of functions, including sleep, mood, appetite, and pain sensation. It consists of three core components: endocannabinoids (naturally occurring molecules), receptors, and enzymes.

The two primary receptors are CB1, found predominantly in the central nervous system, and CB2, located mainly in the peripheral immune system. The two most studied phytocannabinoids from the cannabis plant are Tetrahydrocannabinol (THC) and Cannabidiol (CBD). THC is a partial agonist of the CB1 receptor, responsible for the psychoactive effects, whereas CBD has a low affinity for these receptors but acts as an indirect antagonist, often modulating the effects of THC. For an analysis of the various product forms—such as flower, concentrates, and topicals—the Legal Marijuana Market overview provides a technical breakdown of extraction methods and purity standards.

Beyond THC and CBD, the "Entourage Effect" suggests that the myriad of secondary cannabinoids (like CBG and CBN) and terpenes (aromatic compounds) work synergistically to enhance therapeutic outcomes. Research is currently focused on isolating these specific ratios to treat distinct pathological conditions, moving away from a "one-size-fits-all" approach to botanical medicine.