An exhaustive search of the literature finds no deaths induced by marijuana. The US Drug Abuse Warning Network (DAWN) records instances of drug mentions in medical examiners' reports, and though marijuana is mentioned, it is usually in combination with alcohol or other drugs. Marijuana alone has not been shown to cause an overdose death.

Source

Federal Drug Abuse Warning Network (DAWN); also see 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); and US Department of Justice, Drug Enforcement Administration, "In the Matter of Marijuana Rescheduling Petition" (Docket #86-22), September 6, 1988, p. 57.