There is no definitive evidence that implicates marijuana as a "gateway drug." Several government-commissioned analyses have found no evidence supporting the gateway hypothesis, including a 1999 report by the Institute of Medicine: "There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs." And yet this "theory" has been repeated enough times that most people believe it is true.

Furthermore, decriminalizing marijuana separates it from the black market for other illicit substances, decreasing the exposure of marijuana users to harder drugs.