"Today’s marijuana is 300 percent to 800 percent more potent than the pot of yesteryear."
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Marijuana legalization opponent Heidi Heilman says today's marijuana is 300 percent to 800 percent stronger than in the past
Editors note: This item was revised on April 1, 2014 to reflect the fact that increases of 300 and 800 percent represent four- and nine-fold increases respectively. The ruling remains the same.
In the debate over whether marijuana should be legalized, one issue is the question of potency. Critics of legalization argue that the street drug now available for sale is not the marijuana that a lot of baby boomers and Generation Xers have used.
One of them, Heidi Heilman, director of New England field development for Smart Approaches to Marijuana and president of the Massachusetts Prevention Alliance, raised the issue March 13 in a commentary in The Providence Journal.
"Today’s marijuana is 300 percent to 800 percent more potent than the pot of yesteryear," she wrote. "Such dangerous levels of THC heighten mental illness and addiction risks for those who smoke marijuana — especially for kids with developing brains."
THC or tetrahydrocannabinol, available by prescription, is the key active ingredient in marijuana.
It's well established that the potency of marijuana has increased over time. On Jan. 24, PolitiFact national ruled that when former Rhode Island Congressman Patrick Kennedy said that marijuana today is "genetically modified," with THC levels that "far surpass the marijuana" of the 1970s, his statement was Mostly True.
Heilman was being more specific. Because something 100 percent more potent is actually twice as potent, she was saying that the potency of today's marijuana is now four to nine times greater than "yesteryear," a rather vague starting point. Nonetheless, we wanted to see if her statement was on target or her statistic was a bit high.
Heilman was quick to send us several pieces of information.
The first was a graph showing a rapid increase in potency from 1960 to 2011, a 52-year span. It shows the ratio of THC in marijuana going from 0.2 percent to 11.4 percent. That's an increase of 5,700 percent, well outside the range cited by Heilman.
But are those numbers reliable?
The graph says the information came from a study in the Journal of Forensic Science. But that study was published in 2010, and only covered a 16-year period that ends in 2008.
Its authors, researchers at the National Center for Natural Products Research at the University of Mississippi, examined 46,000 samples of marijuana seized during law enforcement raids. They found that the THC concentrations of marijuana had risen by about 171 percent in that time period, well below the 300 to 800 percent increase cited by Heilman.
We also contacted the Drug Enforcement Administration in Boston and Washington and the White House Office of National Drug Control Policy. They referred us back to the research center at Ole Miss, which has been monitoring THC content at least since the early 1970s.
The researchers there sent us copies of their reports, all published in the journal, along with test results that included the most recent data. We also secured some of their quarterly reports.
We found that even though the report Heilman cited didn’t back up her claim, the Ole Miss data did.
YEAR
Tested
% THC
YEAR
Tested
% THC
YEAR
Tested
% THC
1972
34
0.18
1986
1370
2.36
2000
3148
4.92
1973
33
0.22
1987
1550
2.96
2001
2716
5.36
1974
114
0.36
1988
1640
3.18
2002
2413
6.4
1975
149
0.48
1989
1075
3.04
2003
2517
6.31
1976
209
0.98
1990
1108
3.24
2004
2637
7.24
1977
251
1.76
1991
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2148
3.09
2005
3004
7.24
1978
130
1.73
1992
3336
3.08
2006
2891
7.76
1979
220
1.53
1993
3031
3.38
2007
3114
8.74
1980
151
2.15
1994
3024
3.50
2008
2775
8.89
1981
249
2.11
1995
4792
3.77
2009
3079
8.34
1982
435
3.07
1996
2451
4.09
2010
2720
10.7
1983
1145
3.30
1997
2496
4.64
2011
2342
11.13
1984
1030
3.31
1998
2283
4.47
2012
2055
12.3
1985
1449
2.83
1999
2692
4.6
In 2012, the most recent year in which testing has been completed, the average THC concentration was 12.3 percent.
That would be 300 percent higher (or four times stronger) than 1992 levels, when the average was 3.08 percent. And it would be 800 percent higher (or nine times stronger) than the average level of 0.98 percent found in 1976.
How high could the THC content potentially go?
One specimen, seized on Sept. 11, 2007, was found to have a THC content of 37.2 percent.
Our ruling
Heidi Heilman said, "Today’s marijuana is 300 percent to 800 percent more potent than the pot of yesteryear."
Long-term testing shows that, on average, today's marijuana is three times more potent than pre-1993 marijuana and eight times more potent than grass seized in 1976 and earlier.
We rate her claim as True.
(If you have a claim you’d like PolitiFact Rhode Island to check, email us at [email protected]. And follow us on Twitter: @politifactri.)
Our Sources
ProvidenceJournal.com, "Heidi Heilman: Marijuana follows Big Tobacco’s lead," March 13, 2014
PolitiFact.com, "Has the potency of pot changed since President Obama was in high school?" Jan. 24, 2014
Interview and emails, Heidi Heilman, director, New England field development, Smart Approaches to Marijuana, March 18-19, 2014
Emails, Shirley Simson, spokeswoman, National Institute on Drug Abuse and Rafael Lemaitre, White House Office of National Drug Control Policy, both March 21, 2014; Mahmoud A. ElSohly, research professor, National Center for Natural Products Research, University of Mississippi, and Zlatko Mehmedic, principal research and development chemist, University of Mississippi, both March 24, 2014
"Constituents of Cannabis sativa L. XXIV: The Potency of Confiscated Marijuana, Hashish, and Hash Oil Over a Ten-Year Period," Journal of Forensic Sciences, April 1984, accessed March 25, 2014
"Potency Trends of Delta-9-THC and Other Cannabinoids in Confiscated Marijuana from 1980-1997," Journal of Forensic Sciences, January 2000, accessed March 25, 2014
OleMiss.edu, "Potency Trends of D9-THC and Other Cannabinoids in Confiscated Cannabis Preparations from 1993 to 2008," Journal of Forensic Sciences, September 2010, accessed March 25, 2014
"Potency Monitoring Program Quarterly Report Number 123," National Center for Natural Products Research, University of Mississippi. accessed March 24, 2014
CHART INFORMATION: All data are from the Center for Natural Products Research, University of Mississippi. 1972-1981: Journal of Forensic Sciences 1984; 1982-1994: Journal of Forensic Sciences 2000; 1995-2010: Potency Monitoring Program Quarterly Report Number 123; 2011-2012: Personal communication, Mahmoud ElSohly. When data from multiple years were available, the potency measure listed is based on the largest number of samples tested.
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Marijuana legalization opponent Heidi Heilman says today's marijuana is 300 percent to 800 percent stronger than in the past
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