How is marijuana’s potency determined

Drug Policy Question of the Week – 9-6-10

As answered by Mary Jane Borden, Editor of Drug War Facts for the Drug Truth Network on 9-6-10.

Question of the Week: How is marijuana’s potency determined?

The World Drug Report 2009 states,

“The amount of THC in a cannabis sample is generally used as a measure of ‘cannabis potency.’”

As described in that report,

“The secretion of THC is most abundant in the flowering heads and surrounding leaves. The amount of resin secreted is influenced by environmental conditions during growth …, sex of the plant, and time of harvest.”

The report also notes that,

Most data on cannabis potency are derived from the analysis of seized [marijuana] samples. This means that these samples need to be representative of the entire seizure so that inferences and extrapolations can be made.”

As described in a 2004 report from the European Monitoring Centre for Drugs and Addiction,

“Data on the THC content of cannabis products in the USA have been collected by [Dr.] ElSohly et al. (1984, 2000) for many years as part of the University of Mississippi Potency Monitoring Project. Samples were submitted by law enforcement agencies and it is assumed that they are representative of the market.”

To assist data analysis, details concerning the aforementioned environmental conditions, the type of cannabis, and the size of the plant canopy if known accompany the seized samples to a lab at University of Mississippi’s School of Pharmacy. Here they are put through a series of chemical tests to determine their THC percentage, as well as percentages of the cannabinoids, CBD, CBN, and CBC. One of their recent reports read,

“As of March 15, 2009, the Project has analyzed and compiled data on 65,247 Cannabis, 1365 Hashish, and 476 Hash Oil samples.”

That’s since the project’s inception.

These facts and others like them can be found in the Marijuana chapter of Drug War Facts at

Questions concerning these or other facts concerning drug policy can be e-mailed to

is marijuana’s potency determined?