Marijuana Use as a Gateway to Other Drug Use
"There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs."
Janet E. Joy, Stanley J. Watson, Jr., and John A Benson, Jr. Marijuana and Medicine: Assessing the Science Base. Division of Neuroscience and Behavioral Research, Institute of Medicine. Washington, DC: National Academy Press, 1999.