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Cannabis use and its effects on mental health have become a growing area of concern, especially when it comes to psychosis. Research suggests there is a strong link between cannabis use, psychosis symptoms, and the dopamine system in the brain. This article will explain how cannabis may affect the risk of psychosis by changing dopamine activity, focusing on cannabis and psychosis on the dopamine system and related mechanisms. If you’re worried about cannabis use or want to understand the science behind it, this guide will provide clear and useful information for you.
A recent study led by researchers at McGill University and Western University has brought some real answers to light.
Main Results
1. Cannabis Use Disorder Raises Dopamine Activity
People with CUD had clearly higher neuromelanin-MRI signals in the ventral SN/VTA areas of the brain. This means more long-term dopamine activity. These areas are heavily linked to how severe a person’s psychosis symptoms are.
2. Cannabis and Schizophrenia Together Don’t Just Add Up
Interestingly, those with both CUD and schizophrenia didn’t show a simple doubling of dopamine. The effect of CUD was still clear, but schizophrenia didn’t seem to add much extra. This suggests a more complicated relationship, possibly even that the brain “plates out” on dopamine activity at a particular point.
3. Long-lasting Brain Changes
Even after one year, people with CUD still had higher dopamine activity in key brain regions. This suggests brain changes from cannabis are not just a one-time spike but may last a long time, especially with ongoing use.
4. Nicotine Was Not to Blame
Though people with CUD were also more likely to smoke tobacco, the researchers checked and confirmed nicotine wasn’t causing the dopamine spike. The effect was clearly linked to cannabis use.
5. Severity Matters
The higher the neuromelanin-MRI signal, the more severe the cannabis use. This supports a “dose-response” effect, showing that heavier or more regular cannabis use has a bigger impact on the brain’s dopamine system and, in turn, the risk of psychosis.
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Recent studies have uncovered concerning links between the impact of cannabis on young brains and severe mental health challenges. These findings urge greater awareness and call for stronger prevention efforts.
How Cannabis Alters Developing Brains
A groundbreaking study led by Dr. Palaniyappan and her team examined how cannabis use disorder affects the brain. Using advanced imaging techniques, they identified increased markers of dopamine activity in specific brain regions, similar to those observed in psychosis. This research underscores the troubling effects of cannabis on youth, linking substance use to changes in critical brain pathways.
Psychiatrist Dr. Julie Richard highlights the problem, stating, “Exposure to cannabis is changing young people’s brains… young people as young as 13 are presenting with a psychotic episode associated with recent cannabis use.” This stark reality demonstrates how cannabis use during adolescence can heighten the risk of psychosis and other mental health disorders.
Alarmingly, an increasing number of teenagers, some as young as 12 or 13, are presenting with psychotic episodes linked to recent cannabis use. These episodes highlight the immediate risks cannabis poses to mental well-being. Young users often experience more severe and frequent symptoms, which can upend their academic, social, and personal lives.
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“The genotoxicity and neurotoxicity of cannabis with its ongoing epigenetic harms are well established and irrefutable. However, real concerns about the infiltration of such toxins into our food-chain systems is severely under-reported and insufficiently addressed.
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The debate around cannabis legalisation in France remains a contentious issue, with growing public and political interest. Among the voices opposing this shift is the French Academy of Medicine, which has reinforced its steadfast stance against the legalisation of recreational cannabis. Citing robust evidence from other nations that have adopted legalisation, the Academy highlights significant public health risks and underscores the importance of prevention and education.
Public Health Risks Highlighted by the Academy of Medicine
The Academy of Medicine firmly believes that the legalisation of recreational cannabis poses significant health challenges. It recently released a formal statement affirming its opposition, supported by the latest evidence-based studies.
One of the Academy’s primary concerns lies in the impact of cannabis legalisation on road safety. A pivotal Canadian study, published in 2022 in the New England Journal of Medicine, highlighted alarming figures. After cannabis was legalised in Canada, the proportion of motorists hospitalised after accidents who tested positive for tetrahydrocannabinol (THC)—cannabis’s main active ingredient—doubled. This data paints a worrying picture of the potential risks on French roads if cannabis use is legalised.
Another area of concern is mental health. The Academy cited another Canadian study published in the JAMA Network Open in 2025. This research revealed that cannabis-associated schizophrenia cases among hospitalised patients nearly tripled after legalisation. These findings align with the Academy’s emphasis on prioritising public well-being over recreational freedoms.
The French Academy of Medicine has reiterated that legalising recreational cannabis would be a “serious health error.” In a press release, the Academy emphasised that cannabis use is associated with significant risks, including impaired cognitive function, addiction, and mental health disorders. It also highlighted the lack of sufficient evidence to support claims of cannabis’s safety when used recreationally.
Lessons from Legalisation Elsewhere
Countries like Canada and certain US states have become key testing grounds for understanding the consequences of cannabis legalisation. By assessing their experiences, France has a valuable opportunity to evaluate potential risks before implementing similar laws.
Specifically, Canada’s legalisation has served as a cautionary tale, providing evidence of issues such as increased substance misuse and negative health outcomes. These findings are critical as discussions surrounding cannabis legalisation in France gain momentum. Instead of rushing into premature reforms, the Academy urges policymakers to carefully evaluate these findings to safeguard the nation’s health.
Prevention Over Legalisation
The Academy strongly advocates for maintaining the ban on cannabis use and sale in France. The primary focus must be on educating the public, particularly young people, on the potential risks of cannabis consumption.
Investing in comprehensive prevention programmes that include schools, families, and community outreach could reduce demand. The institution insists that well-executed prevention efforts would achieve better results in reducing cannabis misuse than legalisation would.
Cannabis Legalisation in France and the Political Context
The Academy’s renewed opposition to cannabis legalisation comes at a time of growing political discussion on the topic. Recent proposals have suggested a tightly controlled legalisation framework, but these discussions fail to address the significant health concerns raised by experts. The French Academy of Medicine believes that cautious policymaking informed by existing evidence is crucial to safeguarding the nation’s health.
Instead of adopting measures that echo the mistakes of other nations, France has the opportunity to reinforce its commitment to public health. By rejecting legalisation and strengthening prevention efforts, the country can mitigate the risks associated with cannabis use while fostering greater awareness about its consequences.
(Source: WRD News)
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Cannabis policies in the U.S. have seen a dramatic shift over the past few decades. Most states now allow some form of legal cannabis use, even though federal law still prohibits it. This patchwork of regulations has developed with little federal oversight and often without prioritising public health. A new report from the National Academies of Sciences, Engineering, and Medicine, titled “Cannabis Policy Impacts Public Health and Health Equity” (2024), takes a closer look at these changes, exploring their effects on public health and offering well-researched recommendations for improving cannabis policies.
The Current Policy Landscape
As of April 2024, 38 states, three territories, and the District of Columbia have legalised medical cannabis use, while 24 states have authorised adult non-medical use. This evolution began with California’s 1996 medical cannabis initiative and accelerated with Colorado and Washington’s 2012 adult-use legalisation. The report details how these changes were driven by multiple factors, including compassion for patients, skepticism about cannabis prohibition enforcement, potential tax revenue, and increasing concern about racial disparities in cannabis arrests.
The current legal framework remains complex and contradictory. Cannabis continues to be classified as a Schedule I controlled substance under federal law (though rescheduling to Schedule III has been proposed), while states have implemented varied regulatory approaches. Further complicating matters, the 2018 Agriculture Improvement Act (Farm Bill) removed “hemp” from the Controlled Substances Act, creating a largely unregulated market for hemp-derived intoxicating cannabinoids that operates nationwide.
The Evolution of Cannabis Markets and Products
The report documents significant shifts in cannabis use patterns and product types. National survey data show the prevalence of past-year cannabis use among U.S. adults nearly doubled between 2002 and 2022, from 11% to 21.9%. Perhaps most notably, by 2022, more Americans reported daily or near-daily cannabis use than alcohol use at this frequency. Meanwhile, use among youth has remained relatively stable.
Cannabis products have evolved far beyond traditional dried flower. While flower remains the most commonly used product, cannabis concentrates, edibles, and vape oils are increasingly popular, with many consumers using multiple product types. The potency of cannabis products has also increased dramatically. The average THC concentration in seized cannabis flower rose from approximately 4% in 1995 to over 12% by 2014, while concentrates typically contain 60-90% THC.
The report explains how different modes of administration—smoking, vaping, oral consumption—affect the pharmacokinetics of cannabis and its effects. For instance, inhalation delivers THC rapidly to the brain with effects felt within seconds to minutes, while oral ingestion produces delayed and prolonged effects beginning 30 minutes to 2 hours after consumption and lasting 5-8 hours.
Public Health Functions Applied to Cannabis
A central contribution of the report is its application of core public health functions—assessment, policy development, and assurance—to cannabis regulation. The committee found significant gaps in all three areas.
Assessment: Current cannabis surveillance systems are fragmented and inadequate. While various data sources exist, there is limited coordination and standardisation. The report calls for a centralised, adaptable surveillance system that would monitor cannabis cultivation, product sales, use patterns, and health impacts. Such a system would ideally include a surveillance plan, systematic data collection and analysis, regular dissemination of findings, linkage to public health action, and ongoing evaluation.
The Centers for Disease Control and Prevention (CDC) has developed a cannabis strategy, but the report notes it lacks several essential elements, including approaches to data dissemination, clear mechanisms to translate findings into action, and provisions for regular evaluation.
Policy Development
The report documents how the influence of the cannabis industry has affected regulatory decisions, with examples from multiple states where industry lobbying has successfully opposed public health protections such as pesticide restrictions and limits on THC concentration. The committee found limited safeguards against industry influence in most state cannabis regulatory frameworks.
The authors contrast U.S. approaches with more measured models in countries like Canada and Uruguay, which exercise stricter government control over cannabis products and retail. They note that most U.S. states have weak advertising restrictions, allowing extensive marketing that reaches children and promotes high-potency products.
Assurance: Quality control measures for cannabis products vary widely across states. The report recommends adoption of U.S. Pharmacopeia standards, which provide scientifically valid methods for ensuring product identity, composition, and safety.
Training requirements for retail cannabis staff are inconsistent, yet these individuals often serve as trusted sources of information for consumers. The committee recommends mandatory training covering cannabis effects, prevention of sales to minors, warnings about impaired driving, and recognition of signs of customer impairment.
Public education campaigns about cannabis risks are essential but underdeveloped in most states. The report calls for targeted campaigns directed primarily toward parents and vulnerable populations, addressing risks, harm reduction strategies, and safe storage practices.
Health Equity Considerations
One of the report’s most significant contributions is its examination of how cannabis policies affect health equity. The authors analyse three key dimensions: criminal justice impacts, social equity programs, and effects on social determinants of health.
Criminal Justice Impacts
The historical enforcement of cannabis prohibition has disproportionately harmed communities of color. The report notes that racial disparities in cannabis arrests may have actually increased during policy liberalisation, with arrests decreasing for White people while increasing for Black people between 2002-2004 and 2017-2019. These disparities contribute to health inequities, as criminal records limit economic security, employment, housing, and educational opportunities.
A major limitation in evaluating these impacts is the lack of comprehensive data on cannabis arrests and sentencing. The committee recommends that jurisdictions collect and publicly report detailed data on cannabis law enforcement, including specific violations and demographic information.
Social Equity Programs
Most states that have legalised cannabis have implemented social equity measures aimed at helping communities harmed by cannabis prohibition. These programs typically include criminal justice reforms (record relief, resentencing), technical and financial assistance for cannabis businesses, and community reinvestment initiatives.
While well-intentioned, these efforts face implementation challenges. The report emphasises the need for systematic evaluation and revision of social equity policies to ensure they meet their goals without unintended consequences. It specifically recommends automatic expungement or sealing of records for low-level cannabis offenses, noting that petition-based relief systems have proven less effective.
Social Determinants of Health
Cannabis policies affect numerous social determinants of health, including economic stability, education access, healthcare access, neighborhood environments, and social contexts. The report raises concerns that cannabis retailers may be disproportionately located in lower-income communities or communities of color, potentially contributing to health inequities.
Healthcare access is another critical area. The report notes that punitive policies regarding prenatal drug use exist in nearly half of U.S. states, and drug testing in pregnancy is applied inequitably, particularly to communities of color. This may deter pregnant cannabis users from seeking prenatal care, potentially worsening health outcomes.
High-Potency Products and Research Needs
A particular focus of the report is the public health implications of high-concentration THC products. The authors note that the risks associated with THC consumption increase with dose, and legalising high-potency products potentially increases cannabis-related harms. Products containing high THC concentrations have been associated with greater risk of psychosis and cannabis use disorder.
The committee found that more research is urgently needed to understand the relationship between THC dose and adverse effects. It developed a comprehensive research agenda focused on:
- Public health outcomes of different regulatory approaches
- Efficacy of tests for cannabis impairment
- Health effects of cannabis use in specific populations (pregnant persons, youth, veterans, older adults)
- Health risks of emerging synthetic and semisynthetic cannabinoids
- Effectiveness of risk mitigation strategies
The Path Forward
The report makes clear that better application of public health principles to cannabis policy is essential as legalisation continues to spread. The committee offers specific recommendations for federal agencies, state regulators, and other stakeholders:
The CDC should develop best practices for protecting public health in states with legalised cannabis, drawing from tobacco and alcohol policies. These should address marketing restrictions, age limits, retail regulations, taxation, product design, and measures to limit youth access.
Congress should refine the definition of “hemp” to clarify that intoxicating cannabinoids are not exempt from the Controlled Substances Act, addressing the regulatory gap that has allowed unregulated intoxicating products to proliferate.
State cannabis regulators should require training for retail staff and adopt U.S. Pharmacopeia standards for product quality and safety. The report also calls for Congress to remove restrictions that prevent the Office of National Drug Control Policy from studying cannabis legalisation impacts.
Historical Context and Enforcement Patterns
The report provides valuable historical context for understanding current cannabis policies. It traces state cannabis control policies from the 1860s through today, noting that states have historically led the way in cannabis regulation, with federal policies generally following rather than preceding state action.
Particularly informative is the analysis of enforcement patterns over time. Cannabis arrests reached unprecedented levels between 1992 and 2007, driven primarily by possession offenses and marked by significant racial disparities. This period also saw an increase in collateral consequences for drug convictions, including restrictions on access to education, housing, and public benefits.
The committee notes parallels with alcohol prohibition and its repeal, while acknowledging important differences. Unlike alcohol legalisation, which occurred with formal federal approval, state cannabis legalisation exists in tension with federal law. Additionally, alcohol regulation initially included strict controls designed to moderate consumption, while cannabis markets are emerging in a less restrictive regulatory environment.
Methodological Approach and Evidence Review
The committee conducted a thorough evidence review of the public health impacts of cannabis policy, examining 14 systematic reviews. This analysis found limited or suggestive evidence that perceived risk of cannabis use declines after legalisation, adult use increases, traffic collisions increase, and cannabis-related hospital visits increase. For all other outcomes, evidence was judged insufficient.
This cautious assessment reflects the challenges of studying rapidly evolving policies with varying implementation across jurisdictions. The report emphasises the need for better data collection, improved policy analysis databases, and enhanced surveillance systems to support rigorous evaluation of policy outcomes.
Future Implications of Federal Policy Changes
The report discusses potential implications of rescheduling cannabis from Schedule I to Schedule III under the Controlled Substances Act, a change currently under consideration. While rescheduling would reduce research barriers and might affect tax treatment of cannabis businesses, it would not legalise cannabis federally or automatically legitimise state programs.
The authors note that rescheduling would create additional policy complexity. Schedule III substances require FDA approval before prescription, with regulatory requirements that differ significantly from current state medical cannabis programs. How rescheduling would impact these programs remains uncertain and would depend on FDA implementation and court interpretations.
The National Academies report represents the most comprehensive assessment of cannabis policy through a public health lens in decades. It demonstrates that while cannabis legalisation has proceeded rapidly, attention to public health considerations has lagged. By applying core public health functions to cannabis policy and centering health equity concerns, the report provides a framework for developing more effective approaches to cannabis regulation that protect public health while addressing historical injustices.
Source National Academies
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