As the legalization debate heats up in the run-up to Donald Trump’s reclassification of cannabis, an eminent American researcher is shattering a number of preconceptions. During a webinar organized by the federal agency SAMHSA, Johns Hopkins University professor Ryan Vandrey defended a finer, more scientific regulation of cannabinoids, while denouncing the shortcomings of public policies in terms of prevention, road testing and product analysis.
ZEWEED with Marijuana Moments
Legalization does not increase consumption among young people
Ryan Vandrey, an experimental psychologist and behavioral pharmacology researcher at Johns Hopkins, opened his talk with a reminder that cannabis remains the most widely consumed illicit substance in the United States. Yet, contrary to common fears, consumption among young people does not follow that of adults.
“ Consumption among minors is one of the most sensitive subjects linked to legalization “, he explains, ” but the figures show stability, and even a drop in some cases.” Drawing on data from California since 1996, Vandrey asserts that rates of use among 8th, 10th and 12th graders have not budged, and have even been trending downward in recent years.
Delta-8, CBG, HHC: cannabinoids outdo science
For the researcher, one of the main challenges lies in the poor understanding of cannabis-based products. ” The industry is innovating faster than research,” laments the practitioner. Instead of focusing on the simple delta-9 THC content, which legally distinguishes hemp from cannabis in the USA, Vandrey advocates an approach based on the cognitive and behavioral effects of the products.
In particular, he highlights the differences between the dominant cannabinoids: THC and its derivatives (such as delta-8) can cause addiction, withdrawal or cognitive disorders. CBD, on the other hand, shows no signs of addiction or problematic use, even when combined with low doses of THC. CBG, another cannabinoid studied, seems to act in a similar way to CBD.
But delta-8, though psychoactive, remains poorly regulated: ” A double dosage of delta-8 produces the same effects as a standard dosage of delta-9 “, explains Vandrey, while pointing out the regulatory aberration: the former is freely accessible if extracted from hemp, the latter is still classified as a controlled substance.
Saliva tests, blood thresholds: unsuitable tools
Another stumbling block: tests to assess driving ability. Vandrey and his team found that the standard sobriety tests used by police often fail to detect cannabis-induced motor impairment.
Subjects who ingested 25 mg of THC showed clear psychomotor deficits… yet had THC blood levels below the legal thresholds in several states. The reason: oral consumption produces significant effects, but low plasma levels. Conversely, some people who tested positive on a urine screening test had only taken CBD, whose low residual THC content was sufficient to cause a positive result.
Terpenes: real effects or overmarketing?
Long ignored by research, terpenes – the aromatic compounds found in cannabis – are now being promoted by brands for their supposed effects. He cites a study conducted with researcher Ethan Russo, in which the addition of the terpene D-limonene to pure THC reduced anxiety, paranoia and racing heart… without altering the cognitive or physical effects of THC. Conversely, alpha-pinene, often touted as an antidote to forgetfulness or anxiety, showed no significant effect in the trials.
Schizophrenia, THC levels, labelling: avenues to explore
The talk also addressed the controversial links between cannabis and schizophrenia. Despite the doubling of annual consumption in the United States, cases of schizophrenia remain stable. Vandrey acknowledges a correlation between heavy use and early or severe symptoms of psychosis, but causality remains uncertain.
He also highlights gender differences in problematic cannabis use: women become dependent more quickly, have more withdrawal symptoms and respond less well to treatment.
Another crucial point: product potency is not synonymous with impact. “It’ s the dose that counts, not the concentration,” says Vandrey, describing the phenomenon of self-titration. Experienced users will naturally adjust their intake, whatever the THC content. Diet also influences absorption, especially by the oral route: a fatty meal clearly increases the bioavailability of cannabis, unlike most drugs.
Beyond these observations, the researcher calls for a reform of cannabis regulation, based on objective criteria: formulation, route of administration, real effects, dosage. He also calls for better supervision of retail products, and more resources for research.
” We need to move away from a global regulation of cannabis and think in terms of the type of product: THC-rich cannabis, CBD-rich cannabis, or something else. Otherwise, we’ll miss the real issues. “insists the psychologist.
One plant, a thousand molecules: science continues to unravel the mysteries of cannabis
The last point raised is the rapid evolution of research into the chemical composition of cannabis. Recent studies have highlighted new compounds, such as cannabielsoxa, and novel aromatic profiles linked to genetics, cultivation or drying.
A May 2025 study identified 33 genetic markers strongly influencing cannabinoid production, including a massive set of genes associated with THC-rich varieties.
These advances pave the way for precision genetic breeding programs to develop varieties with targeted therapeutic profiles.
But one doubt hangs in the air: federal policy, especially under the Trump administration, could put the brakes on this momentum. The word “marijuana” is now one of a score of topics deemed “sensitive” by the National Cancer Institute, requiring prior hierarchical validation before publication.
At a time when cannabis is gaining ground in American legislation, science is struggling to keep pace with the industrialization of the sector. Vandrey’s plea is a reminder of the urgent need for more detailed, data-driven regulation, and for research capable of sorting out placebo effects, marketing and therapeutic potential.
