In a powerful presentation for the IASIC Speaker Series, Dr Yasmin Hurd, Ward Coleman Chair in Translational Neuroscience at Mount Sinai’s Icahn School of Medicine, delivered compelling evidence on how cannabis exposure during pregnancy and adolescence fundamentally alters brain development. Moreover, her research demonstrates how this exposure increases psychiatric vulnerability across the lifespan.

The Complexity Behind Today’s Cannabis

Dr Hurd began by addressing a critical misconception: cannabis is not the benign substance many believe it to be. In fact, modern cannabis products contain over 500 chemical compounds, with THC concentrations reaching unprecedented levels—up to 90% in some concentrates and vaping products. Furthermore, this represents a dramatic shift from historical cannabis use, with flower potency alone now averaging 24% compared to significantly lower levels in previous decades.

“The endocannabinoid system is a key modulator of numerous biological functions,” Dr Hurd explained. “When we introduce high-potency THC during critical developmental windows, we’re not just affecting the brain—we’re impacting energy metabolism, immune function, neurodevelopment, pain regulation, stress response, and even reproduction.”

Developmental Cannabis Exposure Reshapes the Foetal Brain

Dr Hurd’s research team has documented profound changes in foetal brain structure following prenatal cannabis use. Specifically, using both human placental tissue and animal models, her laboratory identified significant alterations in the cytoskeleton—the structural framework of developing neurons—alongside disruptions to critical neurotransmitter systems including dopamine and opioid peptides.

Most striking were the immune-related changes discovered in the placenta. “No matter how we analysed the data, these immune alterations emerged robustly,” Dr Hurd noted. In addition, the research revealed that male foetuses showed particularly pronounced changes, suggesting sex-specific vulnerability to developmental cannabis exposure.

These placental changes proved prophetic. Indeed, in longitudinal studies tracking children exposed to cannabis in utero, Dr Hurd’s team documented elevated stress hormone levels, increased aggression, heightened anxiety, and greater hyperactivity by ages three and four. Notably, when maternal cannabis use coincided with significant prenatal stress—such as during Superstorm Sandy in New York—the effects intensified dramatically, with some children receiving earlier psychiatric diagnoses.

The Adolescent Brain Under Siege

Adolescence represents another critical vulnerability window for cannabis exposure. As Dr Hurd emphasised, whilst adult substance use disorders typically begin during adolescence, adolescent cannabis use specifically represents the highest risk period for developing cannabis use disorder.

The statistics are sobering: approximately 30% of cannabis users develop cannabis use disorder—a rate comparable to opioids. Similarly, recent Danish research demonstrated that cannabis use disorder contributed to nearly 30% of preventable schizophrenia cases, with males showing disproportionately higher risk.

“You don’t need to wait until a young person meets clinical criteria for cannabis use disorder to see significant problems,” Dr Hurd cautioned. “We’re now identifying ‘non-disorder cannabis use’ amongst adolescents—substantial consumption causing mental health issues, cognitive impairment, and academic decline without meeting formal diagnostic thresholds.”

Her research using animal models revealed that adolescent THC exposure causes dramatic reorganisation of gene expression in the prefrontal cortex—the brain region responsible for decision-making, impulse control, and emotional regulation. These changes mirrored patterns observed in individuals diagnosed with schizophrenia, suggesting common biological mechanisms linking developmental cannabis exposure to psychiatric disorders.

Epigenetic Mechanisms: How Cannabis Rewrites Development

Perhaps most alarming, Dr Hurd’s work has identified epigenetic mechanisms—environmental modifications to gene expression—that maintain the effects of developmental cannabis exposure throughout life. These molecular “tags” essentially create an environmental memory, keeping genes inappropriately activated or suppressed long after cannabis exposure ends.

“We can normalise behaviour in our animal models by targeting these epigenetic marks,” Dr Hurd explained. “This proves these mechanisms are causal—directly linking prenatal cannabis use to adult psychiatric outcomes.”

The research documented that these epigenetic changes particularly affect immune-related genes in the brain, creating lasting alterations in stress response, decision-making capacity, and vulnerability to addiction.

High-Potency Products Amplify Risk

Dr Hurd addressed the dangerous myth that teenagers moderate their use of high-potency products. “Adults don’t even titrate their use properly—and that’s the real issue,” she stated. Her research demonstrated dose-dependent effects, with high-dose THC exposure during adolescence producing elevated stress hormone levels persisting months after final use, impaired decision-making on gambling tasks, and increased impulsivity under stress.

These neurobiological changes have practical consequences. Cannabis use fundamentally alters the endocannabinoid system—our natural biological mechanism for regulating stress response. Frequent cannabis use reduces cannabinoid receptors throughout the brain and body, essentially removing the brake on stress reactions.

“Many cannabis users report that it helps alleviate stress and anxiety,” Dr Hurd noted. “But actually, it does the opposite—developmental cannabis exposure creates poor stress response.”

Beyond THC: The Cannabidiol Alternative

In the final portion of her presentation, Dr Hurd discussed cannabidiol (CBD), a non-intoxicating cannabinoid showing therapeutic potential. Her research demonstrated that CBD reduced heroin-seeking behaviour in animal models and, in double-blind placebo-controlled human trials, decreased craving, anxiety, cortisol levels, and heart rate responses to drug cues in individuals with opioid use disorder.

“The cannabinoids are not equal,” Dr Hurd emphasised. “When we talk about cannabis today, we’re predominantly discussing high-THC products impacting developmental processes. There may be other cannabinoids with therapeutic applications for psychiatric disorders, though I wouldn’t recommend CBD during pregnancy.”

Critical Implications for Prevention

Dr Hurd’s research carries profound implications for prevention efforts. With near-daily cannabis use now exceeding near-daily alcohol use in the United States—an outcome “nobody expected would ever happen”—and increasing normalisation through legalisation, understanding developmental vulnerability becomes paramount.

The evidence demonstrates that early cannabis exposure matters, potency matters, frequency matters, biological sex matters, and psychiatric comorbidity matters. Environmental stress amplifies risk, creating synergistic effects that dramatically worsen outcomes.

“We need to stop thinking about cannabis as a single substance,” Dr Hurd concluded. “In the real world, I know it’s difficult, but we need to focus on cannabinoid exposure—specifically high-THC products affecting critical developmental processes.”

For researchers, clinicians, educators, and prevention advocates navigating the evolving cannabis landscape, Dr Hurd’s presentation offers essential scientific grounding. Her work demonstrates that developmental cannabis exposure isn’t merely associated with psychiatric risk—it fundamentally reshapes brain biology through mechanisms we’re only beginning to understand, creating vulnerabilities that persist across the lifespan.

The IASIC platform continues to provide vital education on substance use prevention, offering evidence-based insights from leading researchers worldwide. Dr Hurd’s work exemplifies the calibre of scientific expertise supporting prevention efforts in an era of increasing cannabis normalisation.

Source: YouTube