While no one is exactly sure how strong cannabis was in the 1970s, one thing most people agree on is that levels of tetrahydrocannabinol (THC), the main psychoactive compound in cannabis, have increased dramatically—or even exponentially—since that time. As high-potency cannabis flower has given way to even more potent cannabinoid concentrates and extracts, discussion has turned to the possibility of limiting THC content in cannabis products to protect consumers from high doses of the ingredient.
The good news about THC is that in adult users, it’s rarely associated with adverse medical effects. This is the reason for the distinction many cannabis users and industry insiders make between the term “overdose” (applicable to potentially fatal or physically health-risking drugs like opioids or cocaine) and the recent term “green-out” (meaning an excess dose of THC leading to acute discomfort and disorientation). The bad news is that a large dose of THC has the potential to leave users suffering through hours of confusion and terror, even while presenting little physical threat.
With those concerns in mind, many states have started to crack down on the potency of infused cannabis foods by imposing “potency caps,” which refer only to the potency of THC (rather than cannabidiol [CBD], for example), since that cannabinoid is responsible for psychoactive effects and, likewise, is responsible for the discomfort associated with an uncomfortably large dose.
THC Potency Limits
Colorado was the first U.S. state to experience national pushback for its “wild west” climate of unregulated products and, accordingly, the state was early to adopt regulations to control edibles. In 2017, Colorado banned edibles that could be confused with candy and limited edible products to a maximum 800 mg of THC per package.
As of 2021, many other states have implemented THC caps on edibles that are between 50 mg and 100 mg per package; at the same time, Colorado has dialed down its maximum limit into that range. However, other states, such as Illinois and Montana, have per-package limits as high as 500 mg and 800 mg, respectively. Most states mandate a maximum serving of 5 mg to 10 mg but allow many servings per package. (A chocolate bar containing 100 mg will be broken down into 10 squares, each containing 10 mg of THC.) The most extreme approach comes from Canada, where federal regulator Health Canada has capped edibles potency nationally at 10 mg of THC per package.
Who Is at Risk from Edibles?
The urge to protect children comes from legitimate concerns, says Daniele Piomelli, PhD, the Louise Turner Arnold Chair in the Neurosciences and Director of the Center for the Study of Cannabis at University of California, Irvine. “Doing no harm is the first thing one must always think about: The Hippocratic oath of ‘Do No Harm’ is also a good strategy in life,” he says. “To do no harm with THC, the first thing one must do is identify vulnerable populations: groups of folks who are at risk of developing toxicity if they’re exposed to high doses of THC.”
One group we know can be adversely affected by high doses of THC is teenagers still undergoing brain development in regions of the cortex full of cannabinoid receptors. A second group, pregnant women, may also be adversely affected by THC. Among teenagers, the research is fairly stark. “We have substantial data from animal work, but also epidemiological data from human populations, giving the sense that [teenagers are] a population that should be warned against excessive use of THC,” Dr. Piomelli concludes. “[Teenagers] should not see high levels of THC, ever, or if they do, they should take that only very occasionally.”