Unlike caffeine, most evidence suggests that marijuana is not physically addictive. Physical addiction to a drug is caused by the drug physically altering one’s brain chemistry in a way that nurtures dependence. For example, the brain is not accustomed to caffeine. The dependence one develops comes from his brain attempting to compensate for the unnatural chemical reaction.
Since the human brain is already attuned to receive cannabinoids, it does not alter a user’s brain chemistry in any significant way. The binding of cannabinoids to the CB1 and CB2 receptors is an entirely natural chemical reaction. Dr. Jack Henningfield from the National
Institute of Drug Abuse made a chart rating the addictiveness of various substances. On it, he rated marijuana as less addictive than caffeine.