It’s a well-worn platitude, often used by opponents of cannabis legalization: “Today’s marijuana is way stronger than that grass your mom and I used to smoke back in the day.”

There’s actually some truth to the cliché, according to a long-running study at the University of Mississippi — but critics say those findings should be taken with a grain of salt.

Mahmoud ElSohly, a professor of pharmaceutics, runs the potency monitoring project at Ole Miss. Since 1975, ElSohly’s lab has received and analyzed tens of thousands of cannabis samples from across the U.S. All the samples were obtained through seizures by law enforcement, then tested for levels of seven different cannabinoids, including THC, which is considered a proxy for potency.

From the early 1970s through the 1980s, THC levels measured by the project increased slowly, from about one per cent THC to between three and four per cent. 

The latest paper by ElSohly and his team covers confiscated cannabis from 1995 to 2014. In 1995, the average amount of THC per sample was about four per cent. By 2014, it was almost 12 per cent.

“There is a continuous increase, it will climb up and then level for a little bit, maybe a year or two years, and then climb up again and so on,” said ElSohly in an interview.

In part, said ElSohly, the increasing potency of these samples can be attributed to a change in the forms of cannabis that were being seized by police and submitted for testing.

Over time, those more potent sinsemilla samples — undiluted by relatively inert plant materials such as leaves and stems — made up more and more of ElSohly’s database.

Still, ElSohly said, even comparing just the sinsemilla samples over time still shows an increase in potency that he attributes to “a definite selection process” by illicit cultivators trying to grow the most effective product.

ElSohly acknowledges that the samples he receives from law enforcement aren’t a perfect representation of cannabis potency across the U.S. Under his agreement with the U.S. Drug Enforcement Administration, ElSohly is only allowed to test seized, illegally produced cannabis, and can’t touch any products from legal U.S. jurisdictions such as Colorado or Washington.

Contemporary cannabis from those legal jurisdictions can be quite potent, however. Step into any Colorado dispensary, and you’ll easily find strains boasting THC content from 20 to 30 per cent. Concentrated cannabis products such as “shatter” can have THC levels that are even higher.

Some skeptical of projects

Not everyone is convinced that ElSohly’s potency monitoring project has accurately measured the increase in THC over time.

Paul Armentano, deputy director of the pro-legalization National Organization for the Reform of Marijuana Laws, doubts that average THC levels in the 1970s were really as weak as one per cent, describing that number as “ridiculously low,” and suspects those figures may have been skewed by small sample sizes for early samples.

“If the average Americans in the 1970s only had access to one or two per cent (THC content) marijuana, I don’t think marijuana would have been particularly popularized in American culture,” said Armentano. “People would have said, ‘What’s the fuss about?'”

Still, Armentano does believe the average potency of cannabis in the U.S. has increased over time.

“Obviously, there has been an increase in the understanding surrounding cultivating marijuana. And with that increase in understanding and increase in proficiency, we have seen some change in the quality of the product.”

Armentano believes claims of ultra-potent pot play an important role in prohibitionist arguments against the drug in the United States.

“If the average Americans in the 1970s only had access to one or two per cent (THC content) marijuana, I don’t think marijuana would have been particularly popularized in American culture.” – Paul Armentano, deputy director of the pro-legalization National Organization for the Reform of Marijuana Laws

“Because, remember, in the United States we live in a country where over half the country has acknowledged using marijuana. So when those people are told that marijuana is this sort of boogeyman substance, and that does not comport with their own first-hand experience, they’re going to be skeptical.”

By claiming that today’s cannabis is fundamentally different than the cannabis of the past, argues Armentano, prohibitionists are trying to convince boomers that their previous experience with marijuana “is no longer valid.” 

If cannabis is stronger, might people just use less?

Skeptics such as Armentano also point out a potential flaw in the “superweed is more dangerous” argument: If the substance is more potent, users can simply use less to achieve the desired effect.

Carl Hart, a well-known drug researcher who chairs the department of psychology at Columbia University, says he’s seen this effect first-hand while performing studies in which joints that have different potencies are administered to experienced cannabis users.

If a user is given a joint with two per cent THC and a joint with 10 per cent THC, “they just smoke more of the two per cent cigarette versus the 10 (per cent),” said Hart.

Hart says he’s observed this phenomenon even when trying to get test subjects to take a standardized dose of a joint by inhaling for a specific amount of time.

“When you do this sort of thing, if the cigarette is strong, they make the adjustment even when you’re trying to force them to be consistent.”

Hart points out, though, that this is just anecdotal observation. To his knowledge, no one has done a controlled study of whether cannabis users will use less of a more potent strain.

solomon.israel@freepress.mb.ca  @sol_israel