Marijuana Potency Claims Unfounded

Study Says "Claims ... about a 20- or 30-fold increase in cannabis potency and about adverse mental health effects are not supported by the evidence"

Sydney, Australia:  Allegations of a dramatic increase in worldwide marijuana potency are not supported by available evidence, according to a literature review to be published in the journal Addiction.

Investigators at the University of New South Wales, National Drug and Alcohol Research Center, conducted a meta-analysis of worldwide trends in cannabis potency.  Researchers reviewed nine international studies, which analyzed the potency of more than 100,000 marijuana seizures over a period of three decades.

"Increased potency has been observed in some countries, but there is enormous variation between samples, meaning that cannabis users may be exposed to greater variation in a single year than over years or decades," authors concluded.  "Claims made in the public domain about a 20- or 30-fold increase in cannabis potency and about the adverse mental health effects of cannabis contamination are not supported currently by the evidence."

The study criticizes a 2006 United Nations" report that claimed, "[T]oday, the characteristics of cannabis are no longer that different from those of other plant-based drugs such as cocaine and heroin."

A previous study of European marijuana potency trends published by the European Monitoring Center for Drugs and Drug Addiction reported: "There is no evidence of a significant increase in potency.  ... [The] effective potency of cannabis in nearly all EU countries has remained quite stable for many years, at around 6-8 percent THC."

Earlier this month, British Prime Minister Gordon Brown called on Parliament to recriminalize pot possession, alleging that the potency of cannabis had increased to "lethal" levels.

For more information, please contact Allen St. Pierre, NORML Executive Director, at (202) 483-5500, or Paul Armentano, NORML Deputy Director, at: paul@norml.org.  Full text of the study, "Cannabis potency and contamination: a review of the literature," will appear in Addiction.