Walk down any commercial corridor in San Francisco, from the Mission to the Marina, and you’ll see how cannabis has woven itself into the city’s landscape.
Since Proposition 64, dispensaries have become as common as taquerias, and their products have gone mainstream. SF boasts 55 legal dispensaries, according to the SF Office of Cannabis.
But it’s the quieter revolution happening in corner stores, gas stations, and online shops that deserves our attention: the explosion of CBD and other hemp-derived products, often sold with minimal regulation and marketed with a wellness halo, frequently to a younger crowd on social media.
Recent findings from UCSF neuroscience research underscore a troubling gap between the widespread perception of these products as “safe” and the emerging evidence of their risks to the developing adolescent brain.
While adults can make their own informed choices, the reality is that San Francisco’s youth have easy access to these products.
Our UCSF research team specializes in the effects of anesthetics on developing brains. Recently, we have examined what CBD does to the brains of laboratory rats. Rats aren’t humans, of course, but the work is adding biological insight and potentially explaining what we’re observing in humans.
San Francisco was out in front regulating youth vaping. We believe it’s time for the city to acknowledge another danger to its youth.
Update, 8/28/25: We updated the exact number of legal dispensaries as provided by the SF Office of Cannabis.
The myth of a youth-proof system
A common belief is that California’s regulated cannabis system is a fortress against underage use. It is not. While licensed dispensaries should be commended for their high rate of checking IDs at the point of purchase, a landmark recent study revealed a systemic flaw: 85 percent of dispensaries check identification only after a customer has entered the main retail space. This practice exposes any young person who walks through the door to a full suite of cannabis products and marketing before their age is ever verified.
More concerning, however, is what happens when teens try to buy cannabis themselves. According to the California Department of Public Health’s 2022 survey, of the underage youth who reported buying cannabis, an alarming 41 percent said they purchased it themselves from a “store or dispensary.” This isn’t speculation; it’s documented evidence that the system is more porous than we think.
Beyond the licensed “front door,” a far more chaotic and unregulated “side door” has been thrown wide open by a federal loophole.
The 2018 Farm Bill, which legalized industrial hemp, inadvertently allowed for the creation of intoxicating products like THC and THCA, which are chemically synthesized from legal hemp. These products, often sold in vapes and edibles that appeal to youth, are untested, dangerously potent, and sold in smoke shops and convenience stores with little to no age verification.
The lack of enforcement is a documented local problem. Last year, Gov. Gavin Newsom signed an emergency ban on these products, yet they remain stubbornly available. An investigation found that despite the ban, the products remained widely available in Bay Area smoke shops, including in San Francisco.
The adolescent brain is in a unique state of flux. This developmental process makes it highly sensitive to neuroactive compounds like CBD.
The report revealed that local police lack the resources to investigate, and state agencies have taken a slow, “education-first” approach instead of a swift crackdown. The problem is so severe that State Sen. Scott Wiener, who represents San Francisco, introduced legislation this year to combat the online sale of these products, which he noted are sold with no age verification.
This situation is eerily familiar. San Francisco has been at the epicenter of the fight against youth vaping, leading high-profile lawsuits against Juul and passing a landmark ban on e-cigarette sales to combat what officials called a youth epidemic. The rise of unregulated, intoxicating cannabinoid vapes sold in the very same stores represents a dangerous sequel to that public health crisis.
The risks are not limited to teens. Across the country, pediatric hospitals are reporting steep increases in accidental overdoses among young children who unknowingly ingest edibles or other cannabis products left within reach at home. In other words, the same lack of regulation and clear safety standards that threaten adolescents is also putting much younger children at risk inside their own homes.
From lab bench to human impact
As scientists, we share the conviction that animal research should not be hyped. But in the case of our animal brain studies, we believe our findings on CBD are complementary to what we are already seeing in human observational studies. Those studies show what is happening when young people expose themselves to CBD. Our work is showing the biological mechanisms of how something is happening.
This is the picture that’s emerging: the adolescent brain is in a unique state of flux, undergoing a massive reorganization that continues until about age 25. This developmental process, especially in the prefrontal cortex — the brain’s hub for decision-making, social behavior, and emotional control — makes it highly sensitive to neuroactive compounds like CBD.
The Sall Lab has found that repeated exposure to CBD during adolescence led to lasting changes in rats, including dampened social behavior, increased anxiety, and fewer neural connections in the brain’s decision-making center, the medial prefrontal cortex. These findings don’t exist in a vacuum. They strongly mirror the results of human research on adolescent cannabis users.
- Changes in brain structure: Our finding of altered neural architecture is a direct parallel to what neuroimaging studies have documented in human teens. A major long-term study published in JAMA Psychiatry found that cannabis use was associated with accelerated, dose-dependent thinning of the prefrontal cortex in adolescents. Other UCSF research has linked continued use to altered brain connectivity and lower IQ over time.
- Dampened social behavior: Our observation of reduced social interest in animals aligns with psychosocial outcomes in humans. A large-scale study of twins found that adolescent cannabis use was linked to more social problems in adulthood, including loneliness and lower life satisfaction.
- Altered emotional responses: The increased anxiety we saw is consistent with the complex link between adolescent cannabis use and anxiety disorders. The CDC lists an increased risk of mental health issues, including depression and social anxiety, as a key negative effect of teen cannabis use. While some teens may believe cannabis helps their anxiety, prospective studies suggest it may actually worsen symptoms over time.
This evidence is why the nation’s leading pediatric health organizations are sounding the alarm. The American Academy of Pediatrics is unequivocal, stating that people under 21 should not use any form of cannabis. The organization explicitly warns that “natural” does not mean “safe” and stresses the profound lack of evidence for the beneficial use of commercial CBD products in children.
San Francisco’s next conversation
The evidence is clear. Our youth have documented access to a vast and poorly regulated cannabis market, and a convergence of human and laboratory science says the risks to their developing brains are real.
This isn’t an argument for a new prohibition. It is a call for a more honest and evidence-based conversation. We need to equip parents, educators, and teens themselves with clear information, free from marketing hype.
Our city has always been at the forefront of public health, from HIV/AIDS to tobacco control. It can and should lead on this issue as well. We must bridge the dangerous gap between what is being sold to our children and what science is telling us. The health of the next generation of San Franciscans depends on it.
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