Legal marijuana products contain extraordinary levels of THC, which could cause dependence and mental health issues with habitual use.

The marijuana you see in stores today isn’t like what the hippies rolled in the 70s. If you follow cannabis news, you have likely heard some version of that sentiment by a public health official. Last year, U.S. Surgeon General Jerome Adams claimed that today’s cannabis “ain’t your mother’s marijuana” but was three times stronger than weed in the 1990s.

Marijuana advocate and Canadian author Dana Larsen actually calculated how strong today’s cannabis would be if you accepted similar lawmaker sentiments throughout history. That includes claims by 2002 White House Drug Czar John Walters, who said that cannabis at the time was 30 times stronger than what baby boomers smoked, and current Democrat presidential nominee Joe Biden, who once argued that comparing 1990s weed to cannabis in the 60s was like “comparing buckshot in a shotgun shell to a laser-guided missile.”

Using all of these historical statements would mean that today’s cannabis is 12,600 times stronger than it was in the 60s, according to Larsen’s calculations. And while that is highly unlikely, we shouldn’t discount how and why cannabis potency has changed in the past decade or so.

The Colorado Department of Public Health and Environment (CDPHE) released a study last week that examined THC concentrations of weed products sold in legal dispensaries. The report was requested by the Colorado General Assembly. Longitudinal reports like this that are focused on markets in Colorado and Washington provide great insight into the state of legal weed and its effects on consumers, as the two states were the first to legalize recreational cannabis.

Growers in both illicit and legal markets have emphasized THC potency over the past 25 years, as consumers associate higher THC levels with getting the most bang for their buck. A 2016 study found cannabis samples seized by the DEA increase from about 4% THC in the 1990s to approximately 12% in 2014.

But the recent CDPHE report noted that cannabis flower in Colorado contained an average of 19.6% THC per gram with potency reaching 35% in some strains. A 2020 study added that over 92% of products sold in retail marijuana stores contain THC levels at 15% or higher. Edible potency actually decreased because Colorado regulators instituted policy changes that set maximum THC concentration to 10 mg per dose, and only allowed 100 mg THC per package.

Those who consumed THC concentrates (i.e. dabbing) used cannabis more frequently day to day compared to flower users.

Previous research found that THC levels in medical marijuana products were two to three times stronger than what doctors recommended for pain relief patients. The study’s authors noted that levels up to 5% THC were sufficient in long-term pain management with minimal side effects.

When THC is too strong, it can lead to dependence problems for users. A recent study noted that 30% of marijuana users have some form of cannabis use disorder. Research published in May added that high-potency cannabis doubles your risk for developing anxiety disorders.

“Our ability to make unbiased, evidence-based statements on the potential health effects of marijuana products containing high THC concentration is limited until further scientific research can be conducted and the evidence shared or published,” the CDPHE report’s authors concluded. “Therefore, in the best interest of public health, we suggest funding research to answer these questions.”