[Editor's Note: The University of Mississippi's Potency Monitoring Project (UMPMC) tested seized marijuana from all 50 states to determine the percentage of THC, the primary psychoactive ingredient in marijuana.
The highest tested sample had 22.04% THC (domestic) and 27.30% THC (nondomestic). The highest tested sample ever tested between 1975 and 2009 had 33.12% THC (domestic) and 37.20% THC (nondomestic).
For comparison, the national average of marijuana's THC content in 1978 was 1.37%, in 1988 it was 3.59%, in 1998 4.43%, and in 2008 8.49%.
Although average potencies have increased, the National Institute of Drug Abuse (NIDA) reported in the June 4, 2002 Washington Post article "The Real Dope: Tried the 'Today's Pot Is Stronger' Claim With Your Kids? Your Cover Is Blown" that "joint sizes have dropped over the years from half a gram to about a quarter of a gram." In addition, pipes, water pipes, and vaporizers typically require less marijuana per use than joints and these items have become increasingly popular over the last 30 years. Some medical marijuana advocates contend that more potent marijuana means less marijuana is needed to achieve the desired medical benefit.
Is Marijuana Significantly More Potent Now Than in the Past?
Andrea Barthwell, MD, former Deputy Director at the U.S. Office of National Drug Control Policy (ONDCP), told an audience on Jan. 26, 2005:
"[I]n the 1970s and 80s, the active ingredient in marijuana, THC, was at 3.5 percent. Today, the THC found in most marijuana averages more than 7 percent. But specific techniques can skyrocket the amount of THC to as high as 27 percent.
The higher the THC gets, the more rapidly you deliver a large jolt of the active ingredient to the brain. Today's marijuana is much more powerful and much more addictive than it was a generation ago."
Mahmoud A. ElSohly, PhD, Research Professor at the Research Institute of Pharmaceutical Sciences at the University of Mississippi, stated in a 2000 Journal of Forensic Sciences article titled "Potency Trends of Delta-9-THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997":
"The potency (concentration of D9-THC) of marijuana samples rose from less than 1.5% in 1980 to approximately 3.3% in 1983 and 1984, then fluctuated around 3% till 1992. Since 1992, the potency of confiscated marijuana samples has continuously risen, going from 3.1% in 1992 to 4.2% in 1997. The average concentration of D9-THC in all cannabis samples showed a gradual rise from 3% in 1991 to 4.47% in 1997.
Hashish and hash oil, on the other hand, showed no specific potency trends. Other major cannabinoids [cannabidiol (CBD), cannabinol (CBN), and cannabichromene (CBC)] showed no significant change in their concentration over the years."
The European Monitoring Centre For Drugs and Drug Addiction (EMCDDA), in their July 2004 report titled "An Overview of Cannabis Potency in Europe" noted the following:
"The available data do not show any long-term marked upward trend in the potency of herbal cannabis or cannabis resin imported into Europe.
The effective potency in nearly all countries has remained quite stable for many years at around 6-8%. The only exception has been the Netherlands where, by 2001-2002, it had reached 16%.
In the United Kingdom, the amount of herbal cannabis or cannabis resin in cannabis cigarettes has shown no trend in the last twenty years.
Statements in the popular media that the potency of cannabis has increased by ten times or more in recent decades are not supported by the limited data that are available from either the USA or Europe. The greatest long-term changes in potency appear to have occurred in the USA. It should be noted here that before 1980 herbal cannabis potency in the USA was very low by European standards.
The THC content of herbal cannabis [in the USA] increased from around 1% before 1980 to around 4% in 1997...
[I]t must be assumed that the quality of herbal cannabis consumed in the USA more than twenty years ago was unusually poor, but that in recent years it has risen to levels typical of Europe. So even the modest increase found by ElSohly et al. (2000) may be less significant than it seems.
The conclusion of this report is that there have been modest changes in THC levels that are largely confined to the relatively recent appearance on the market of intensively cultivated domestically produced cannabis. Cannabis of this type is typically more potent, although it is also clear that the THC content of cannabis products in general is extremely variable and that there have always been some samples that have had a high potency."
The Drug Policy Forum of Texas stated the following in a booklet titled "Are Texans Being Denied Access to a Vital Medicine," published in June 2002:
"Much has been said about marijuana today being much more potent than in earlier years, most of it wild exaggeration. There has always been a wide spectrum of potency in different strains. The most potent earlier strains were much more potent than the average potency of strains today.
According to the Potency Monitoring Project, a federally-sponsored research program at the University of Mississippi, marijuana potency has risen somewhat, but is less than double what it was 17 years ago.
In 1985, commercial grade marijuana averaged 3.71% THC; in 1998, it had climbed to 5.57%, and by 2000 had dropped to below 5%. Highgrade 'sinsemilla' marijuana (seedless) averaged 7.28% in 1985, climbing to an average 12.32% in 1998."