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Published: 01 June 2026

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Young people who regularly combine cannabis and tobacco face nearly three times the risk of developing a full psychotic disorder. That is the central finding of a landmark study published in Nature Mental Health, and it is one that researchers say demands urgent attention.

Dr Heather Ward at Vanderbilt University led the research. Her team tracked more than 1,000 participants through the North American Prodrome Longitudinal Study. These were adolescents and young adults already flagged as being at “clinical high risk” for psychosis. They showed early warning signs but had not yet developed a condition such as schizophrenia.

A Growing Trend With Serious Consequences

The effects of mixing cannabis and tobacco on mental health have long been overlooked. Exclusive tobacco use has declined over recent decades. Cannabis use has risen sharply. Yet the habit of using both together, called co-use, has grown quietly across the general population. Until this study, its impact on those most vulnerable to psychosis had received very little scientific attention.

The numbers are striking. Among the 734 individuals classed as clinically high risk, those who used heavy cannabis and light tobacco together were 2.93 times more likely to develop full psychosis than those using neither substance. The hazard ratio sat within a 95% confidence interval of 1.23 to 6.97, a result the research team considers statistically robust.

“People with psychosis are much more likely to use cannabis and tobacco than the general population,” said Dr Ward. “Because of their heavy use of both, they are also disproportionately affected by the negative consequences.”

Combining Cannabis and Tobacco Effects: What Happens in the Brain

Combining cannabis and tobacco effects begins at a biological level. Smoking both substances together causes the body to absorb significantly more THC, the primary psychoactive compound in cannabis. The brain then faces a stronger and more concentrated impact than cannabis alone would produce. This can push vulnerable individuals closer to a psychotic episode.

Researchers call this a synergistic relationship. The two substances amplify each other. For adolescents whose brains are still developing, and who may already carry a neurological vulnerability to psychosis, this amplification carries serious consequences.

The researchers did acknowledge an alternative reading. Some individuals who develop psychosis may carry a predisposition that drives them toward using both substances in the first place. Further studies aim to explore that question directly.

Effects of Mixing Cannabis and Tobacco Build Slowly Over Time

One of the more surprising findings is that co-use does not appear to worsen day-to-day psychiatric symptoms in the short term. Participants using cannabis or tobacco alone showed higher rates of anxiety, depression and early psychotic experiences. Those using both together did not score worse on those same short-term measures.

The real danger builds quietly beneath the surface. The effects of mixing cannabis and tobacco accumulate over months and years. The long-term risk of converting to full psychosis rises considerably. This delayed pattern makes the habit particularly hard to identify as dangerous in real time.

A 20-Year Reduction in Life Expectancy

The consequences reach well beyond mental health. For those who have already developed a psychotic disorder and continue to use tobacco, the physical toll is severe. Tobacco use in people with psychosis links to a 20-year reduction in life expectancy. Cardiovascular disease, heart attack, stroke and lung cancer all contribute to that figure.

Tackling co-use before a disorder takes hold is not just about protecting mental health. It is about preserving decades of life.

What This Means for Young People and Families

Research estimates that between 25% and 50% of people in their first episode of psychosis use cannabis. Cannabis use consistently links to more severe symptoms, poorer treatment response and higher rates of psychiatric hospitalisation. Adding tobacco to the picture, this study shows, compounds that risk significantly.

Dr Ward was direct. Clinicians and young people alike need to recognise that combining cannabis and tobacco effects represents a concrete risk factor for psychosis. Stopping both substances already eases short-term symptoms such as anxiety and depression. Researchers believe quitting may also cut the long-term risk of developing psychosis altogether, though dedicated clinical trials will need to confirm this.

The team plans to replicate these findings in other high-risk populations and to test whether quitting both substances produces a measurable drop in conversion rates.

Early Action Offers the Best Chance of Prevention

For adolescents and young adults, the period between early warning signs and a full psychotic disorder is narrow but critical. Understanding the effects of mixing cannabis and tobacco during this window can make a real difference. The brain is still developing. Habits are not yet entrenched. The risk is real but it is also preventable.

The evidence now makes this clear. When young people combine cannabis and tobacco, the danger to their mental health is measurable, cumulative and serious. Acting early, before that risk compounds, remains the most powerful step available.

The study received funding from multiple National Institutes of Health grants and its findings were presented at the Society of Biological Psychiatry Annual Meeting.

(Source: WRD News)

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Published: 28 May 2026

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New research from King’s College London asks one of the most pressing questions in mental health science: why does cannabis use raise the risk of psychosis in some people but not others? Scientists published the findings in Biological Psychiatry: Global Open Science in 2026. They point to a complex web of shared genes and biological pathways that may one day help identify the most vulnerable individuals early.

For anyone who has seen a young person’s mental health deteriorate alongside heavy cannabis use, this research feels significant. It moves the conversation beyond statistics and into biology, offering a clearer picture of what actually happens at the molecular level.

What the Genetics Reveal About Cannabis Use and Psychosis Risk

The team at the Institute of Psychiatry, Psychology and Neuroscience (IoPPN) conducted a large scale genetic analysis drawing on data from over 547,000 participants. Rather than study schizophrenia alone, they built a broader “combined psychosis” group that also included bipolar I disorder. This better reflects how cannabis related psychosis presents in real life.

Their analysis uncovered more than 550 genetic locations linked to psychosis, including 122 entirely new associations. They also found that far more biological pathways overlap between cannabis use disorder and psychosis than chance alone would predict. This strongly suggests the two conditions share genuine biological roots, not simply co-occurring for social or lifestyle reasons.

Using a method called Mendelian randomisation, researchers confirmed that cannabis use disorder causally raises the risk of psychosis. That causal effect ran stronger from cannabis use to psychosis than in the reverse direction.

Three Distinct Routes from Cannabis Use Disorder to Psychosis

At least three separate genetic clusters drive the link from cannabis use disorder to psychosis. Each cluster points to a different biological mechanism, which helps explain why the relationship looks so varied in clinical settings.

The first and third clusters involve genes tied to synaptic signalling and neuronal development. Cannabis may disrupt how nerve cells connect and communicate, especially during critical windows of brain development in adolescence and early adulthood.

The second cluster carries the strongest genetic signals. It connects to intracellular signalling, epigenetic regulation, and gene expression. In plain terms, heavy cannabis use may alter how genes switch on or off. Those changes could contribute to the onset of psychotic illness.

Only one causal cluster ran in the opposite direction, from psychosis to cannabis use. This suggests less biological variation in why people with psychosis might turn to cannabis, which mirrors what clinicians tend to observe.

The Glutamate Connection and Cannabis Use and Psychosis Risk

One system appeared consistently across every analysis: the glutamate pathway. Glutamate is the brain’s primary excitatory neurotransmitter, and scientists have long linked disruption in this system to psychosis.

Genetic scores built around glutamate related genes were the strongest predictors of psychosis across the entire sample. Those scores remained predictive both in cannabis users and in people who had never used the drug, though the effect was particularly strong among users.

THC, the psychoactive compound in cannabis, acts on CB1 receptors that sit on glutamatergic neurons. The research team suggests cannabis may amplify an existing underlying vulnerability in this system, potentially tipping susceptible individuals towards psychosis.

Professor Marta Di Forti, the study’s senior author, put it plainly: genes involved in the glutamate system might one day help identify those at greater risk of developing psychosis when using cannabis.

Why Cannabis Use and Psychosis Risk Research Matters Now

Cannabis sits among the most widely used substances in the world. Debates about legalisation continue across many countries, and that makes understanding who carries the greatest risk far more than an academic exercise.

Among cannabis users, genetic vulnerabilities in neuronal pathways, covering axon development, dendritic structure, and synaptic function, all associated with higher psychosis risk. This raises a real prospect: developing tools that flag high risk individuals before psychosis takes hold.

Biological pathways tied to GABAergic signalling and calcium channel activity lost significance once researchers statistically removed cannabis use from the equation. Those pathways may therefore be specific to cannabis related psychosis rather than psychosis in general. That distinction could eventually point towards more targeted clinical approaches.

What This Research Means Going Forward

This study adds weight to a growing body of evidence. The link between cannabis use and psychosis risk is not simply a lifestyle or environmental story. Genetics play a real part, and the biological picture is becoming clearer.

The study carries important caveats. Researchers drew data almost entirely from people of European ancestry, which limits how widely the findings apply globally. The pathway based genetic scores are exploratory and need replication in larger samples before anyone could use them in practice.

Still, the direction is clear. Science around cannabis use disorder and psychosis is becoming more precise. The hope is that greater precision will eventually translate into better identification of those most at risk and more targeted support for those already affected. (Source: WRD News)

Also See:

• All Young Cannabis Users Face Psychosis Risk
• Cannabis & Psychosis – Irrefutable
• C.I.P – Cannabis Induced Psychosis

 

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Published: 21 May 2026

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Cannabis is the most commonly used illicit substance during pregnancy. Many pregnant people are unsure of the risks or where to turn for support. Researchers are exploring practical, accessible ways to help expectant mothers reduce or stop use. One of the most promising approaches may be as straightforward as putting on a pair of trainers.

A recent study by Cynthia L. Battle and colleagues examined a structured walking programme for pregnant individuals. The goal was to see whether it could help them cut back on cannabis use during pregnancy whilst also supporting their mental wellbeing. The findings are encouraging.

Walking to Reduce Prenatal Cannabis Use: What the Study Found

Researchers recruited 16 pregnant adults between 12 and 25 weeks gestation. They came from OB-GYN clinics in Rhode Island and through online channels. All participants used cannabis at least weekly before pregnancy. They also wanted to reduce or stop use and reported symptoms of depression or anxiety.

Over ten weeks, participants took part in a structured walking programme. Clinicians led six sessions in total, each building on daily step goals from the previous week. Participants also wore Fitbit devices to track their steps throughout.

The numbers tell a clear story. At the start, 62.5% of participants were still using cannabis. By 36 weeks gestation, that figure fell to just 16.6%. Symptoms of depression and anxiety also dropped over the course of the programme and stayed lower at the one month postpartum mark. Attendance was strong too. 88% of participants completed the programme, attending an average of 5.8 out of 6 sessions.

Why Physical Activity Matters for Cannabis Use During Pregnancy

Regular, moderate physical activity is already part of the guidance for a healthy pregnancy. Exercise also has well-established benefits for mood and stress. Both of these matter for pregnant people who may be using cannabis to cope with anxiety or low mood.

Understanding why someone uses cannabis during pregnancy is just as important as encouraging them to stop. For some people, it manages symptoms that feel otherwise unmanageable. A walking programme offers an alternative outlet for stress and anxiety. It addresses the behaviour alongside the underlying need.

Healthcare providers play a key role here. When they understand why a patient may be using cannabis, they can help that person find constructive ways to cope. Physical activity is one such option, and this research shows pregnant people are genuinely willing to engage with it.

Prenatal Cannabis Use Does Not Always Stop After Birth

One finding from this study stands out. Whilst cannabis use during pregnancy dropped significantly, it rose again to 50% at one month postpartum. That is a striking reversal, and it points to something important: support cannot simply end at birth.

The postnatal period brings its own pressures. Without continued guidance, the progress made during pregnancy is hard to maintain. Longer term conversations between providers and patients are essential. Continued awareness of the risks matters too, both for the parent and for the child.

What This Research Means Going Forward

This was a small, preliminary study without a control group. It cannot definitively prove the walking programme caused the reduction in prenatal cannabis use. Participants already wanted to change, which may also have shaped the results. Larger, more rigorous trials are the next step.

Even so, the study makes a useful case. A walking programme costs little, requires no specialist equipment, and carries no known risks during a healthy pregnancy. It also improved mood and reduced anxiety alongside cannabis use. That combination is worth taking seriously.

The conversation around cannabis use during pregnancy needs to be honest and grounded in real support. Research like this moves that conversation forward in a practical direction.

(Source: WRD News)

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Published: 19 May 2026

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Back in 2020, the National Drug Research Institute at Curtin University finally got around to tallying up what cannabis costs in Australia were actually doing to the country. The last time anyone had done this properly was 2007 — thirteen years earlier. The number they landed on for 2015–16? $4.5 billion. In a single year.

It barely made a ripple. And since then? Nobody in authority has bothered to update it.

That’s not an oversight. That’s a choice.

What Did $4.5 Billion Actually Buy Us?

In the 2015–16 financial year, more than 2 million Australians used cannabis. Around 150,000 were clinically dependent on it. And 3,422 adults were serving prison sentences directly attributable to cannabis.

The bill broke down like this:

• $2.4 billion — Crime. Policing ($475M), imprisonment ($1.1 billion), courts, legal aid, crime victims. More than half the total, right there.
• $714 million — Healthcare. Mental health programmes, hospital admissions, psychosis presentations.
• $560 million — Workplace. Absenteeism and lost productivity.
• $470 million — Other social costs, including child protection.
• $194 million — Road trauma.
• $106 million — The intangible cost of 23 people who didn’t come home. Over 850 years of life, gone.

Total: $4.5 billion.

Anyone still want to argue that cannabis is a harmless personal choice with no impact on anyone else? The numbers say otherwise and these are the conservative numbers from nearly a decade ago.

The Counting Stopped. Funny That.

The NDRI had been working through a series of national cost reports — methamphetamine, tobacco, opioids, then cannabis. Solid, rigorous work.

Then it stopped.

In the years since 2016, Australia’s cannabis policy environment shifted dramatically. Decriminalisation pushes. Legalisation campaigns dressed up as social justice. And most significantly — the rapid expansion of dodgy ‘medicinal’ cannabis prescriptions.

It is hard not to notice that the national cost-accounting exercise was quietly wound down at precisely the moment it became politically inconvenient. When the evidence doesn’t fit the narrative, apparently the solution is to stop producing the evidence.

The communities, families, healthcare workers and kids left dealing with the real-world fallout deserve better than that.

‘Medicinal’ Cannabis: Pull the Other One

Here are the actual numbers, because they need to be seen to be believed.

In 2017 there were 231 medicinal cannabis prescriptions in Australia. By January 2024, over one million Australians were using medicinal cannabis products — confirmed by the Australian Health Practitioner Regulation Agency. More than 2.7 million prescriptions have been issued since legalisation, according to TGA data.

Let’s call that what it is: a regulatory loophole that has done more to normalise cannabis use across the broader population than any legalisation campaign could have achieved directly. And — worth noting — there is very little evidence it is even effective for anxiety or chronic pain, which are among the most common conditions it is now prescribed for.

And here’s the thing: the harms don’t care what it says on the packet. The link between cannabis and psychosis was already flagged as clinically significant in the 2015–16 NDRI data — cannabis-related psychosis presentations were the most costly cannabis-related hospital admissions in the country. Nothing since suggests that has improved.

The ‘medicinal’ label does not make the social costs disappear. It just makes them easier to ignore — and harder to count, because we’ve stopped counting.

That $4.5 Billion? Just the Opening Act

The $4.5 billion figure reflects 2015–16. Here’s what has changed since:

The user population has grown. The Australian Institute of Health and Welfare recorded 2.5 million Australians using cannabis in the 12 months to 2022–23 — up from 2 million in the period the NDRI examined. Daily use among recent users has jumped from 14% in 2019 to 18% in 2022–23.

The prescription numbers have exploded — from 231 in 2017 to over one million patients by January 2024.

And the original $4.5 billion was already an undercount. The researchers themselves flagged that the cost of presenteeism — workers turning up impaired — hadn’t been adequately measured and needed further research. Nearly a decade later, that research still hasn’t been done.

Factor in a decade of cost inflation across health, justice, and social services — and that 2015–16 figure looks increasingly like a floor, not a ceiling.

Kids, Families, Communities: That Is Who Is Paying

Behind every dollar of that $4.5 billion is a person. A family. A young person whose developing brain was exposed to a drug that carries real, documented risks — risks that have been systematically downplayed as the normalisation machine has rolled forward.

The child protection cost alone — $470 million — doesn’t exist in a vacuum. It represents kids removed from homes, families fractured, caseworkers overwhelmed. The mental health burden lands on communities that were never resourced to carry it. The road trauma touches families who never saw it coming.

This is not abstract. It is happening in suburbs and country towns across Australia, quietly, expensively, and with no updated national reckoning to show for it.

So Where Does That Leave Us?

Cannabis costs in Australia were $4.5 billion in 2015–16. The user population has since grown to 2.5 million. Daily use is up. Medicinal prescriptions have gone from 231 to over a million. And the national cost-accounting has not been updated once.

That number has not gone down. It has gone up — and nobody in authority is measuring it.

The only honest response is to demand the evidence be updated, the true costs be counted, and policy be built around protecting communities rather than accommodating an industry that profits from permission.

The families, schools, and young people carrying the real costs of this drug already know the answer. It’s time the data caught up.

(Source: WRD News)