From the Editor

Cannabis was the only thing that helped him sleep, my patient explained. He also described positive information he had found online. He then asked: Will it affect my psychosis?

In a new review published in The Lancet Psychiatry, Wayne Hall (of The University of Queensland) and his co-authors look at cannabis use and major mental disorders. The topic isn’t new, of course, but their approach is impressive: they draw on many types of studies (epidemiological, genetic, experimental, and preclinical) to try to establish the connection – or the lack of connection – between daily cannabis use and psychosis, bipolar disorder, anxiety, and depression. “There is credible evidence that regular cannabis use plays a contributory causal role in psychosis.” We discuss the paper and its implications.

How have cannabis and alcohol misuse changed over time? In the second selection, from JAMA Psychiatry, Beth Han (of National Institutes of Health) and her co-authors use a US dataset with almost 190 000 participants, and show a sharp rise in cannabis use disorder. “More effective cannabis use disorder treatments are needed.”

Finally, in the third selection, Dr. Sivabalaji Kaliamurthy (of Howard University) writes about cannabis in an essay for The New York Times. He notes a big increase in the potency of cannabis and describes his worries as a physician, particularly about adolescent users. “The question now is whether we are willing to regulate and enforce product safety, especially to protect the most vulnerable among us.”

DG

Selection 1: “Relationships between cannabis use and mental disorders: assessing the coherence of evidence from studies with different methodologies”

Wayne Hall, Tesfa M. Yimer, Rachel Lees Thorne, et al.

The Lancet Psychiatry, July 2026

Anxiety and depression are the most common mental disorders among young adults globally. Psychotic disorders are less prevalent globally (23.6 million) than anxiety (301.4 million) and depression (279.6 million), but all of these disorders affect the lives of people who develop them…

Cannabis use disorder comprises a problematic pattern of cannabis use that produces clinically significant impairment or distress. Cannabis use disorder is more likely to develop when cannabis use is initiated during adolescence than adulthood and when the person uses daily or near-daily into young adulthood. A systematic review of six longitudinal studies estimated the risk of cannabis use disorder as 27% in young people who have ever used cannabis and 33% among young people who used cannabis at least weekly. This Review prioritises evidence on frequent or regular cannabis use, defined as daily or near-daily use, because it is the pattern most strongly associated with the development of cannabis use disorders and with anxiety, depression, and psychotic disorders.

So begins a paper by Hall et al.

Cannabis use and psychosis

“Prospective studies in Germany, the Netherlands, New Zealand, Sweden, and the UK have assessed associations between daily or near-daily cannabis use in adolescence and young adulthood and the likelihood of receiving a diagnosis of psychosis or reporting psychotic symptoms. A 2024 meta-analysis found that any measure of recreational cannabis use (eg, current use, use ever, lifetime frequency of use) was associated with a three-fold increase in the incidence of psychosis.”

Could this simply be a case of self-medication? “Evidence for the self-medication hypothesis is weak.” They make several comments, including: “epidemiological studies have found that cannabis use more often precedes than follows the onset of psychotic symptoms, and that the relationship persists after controlling for a personal history of psychotic symptoms.”

What about trends in incidence and prevalence? “If there is a causal relationship between cannabis use and psychosis, then one would expect the incidence or prevalence of schizophrenia to increase as the prevalence of cannabis use increases among young adults. Some studies suggest that the incidence of psychoses has increased in locations where the prevalence of cannabis use has increased.” 

They add: “The coherence of evidence supports the hypothesis that regular cannabis use is a contributory cause of psychosis, ie, a factor that acts in conjunction with other risk factors to produce psychotic symptoms.”

Cannabis use and bipolar disorder

“Longitudinal studies indicate that people who have used cannabis have a higher risk of developing bipolar disorders than those who have not… In longitudinal studies of people with bipolar disorders, the frequency of cannabis use at the time of diagnosis predicts the frequency of manic symptoms at follow-up. Cannabis use is also associated with a younger age of onset of mania, more frequent depressive or manic episodes, more severe bipolar symptoms, more rapid cycling or mixed episodes, and less improvement with treatment. Systematic reviews find an association between cannabis use and poor outcomes in people with bipolar disorder.”

They add: “Daily cannabis use might play a contributory causal role in precipitating and exacerbating bipolar disorders, but the evidence is not as strong as that for daily cannabis use and schizophrenia.”

Cannabis use and depressive disorders

“People who have depressive disorders report higher rates of cannabis use disorder and of regular cannabis use than people without depressive disorders, but the strength of association is modest in longitudinal studies. A systematic review estimated the OR of depression among people who use cannabis to be 1.29…” They note some problems with that review. “Systematic reviews of prospective studies of the association between patterns of cannabis use and the clinical course of depressive disorders find that people who are depressed and have cannabis use disorder report more severe symptoms of depression than those without cannabis use disorder. A meta-analysis found a consistent association between cannabis use at baseline among young people and depression at follow-up, which persisted after adjusting for potential confounders.”

They add: “There is unclear evidence on the plausibility of a causal role for regular cannabis use in depression incidence or prevalence.”

Cannabis use and anxiety disorders

“There are very few longitudinal studies of relationships between regular cannabis use and anxiety disorders, and meta-analyses of these studies have come to different conclusions. Gobbi and colleagues reported a meta-analysis of three longitudinal studies of anxiety in young adults in the USA. They found no significant increase in the risk of anxiety disorders among people who used cannabis (OR=1.18)… Burke and colleagues conducted a systematic review and meta-analysis of longitudinal studies of general population samples that assessed cannabis use and anxiety disorders, including only studies that excluded participants with anxiety symptoms at baseline. Cannabis use was not associated with incident anxiety disorder in estimates from seven studies (risk ratio=1.10)…”

They add: “Overall, some studies have reported modest associations between cannabis use and anxiety disorders. Few have assessed the regularity of use. These modest associations might reflect shared risk factors…”

A few thoughts:

1. This is a good paper on an important topic, published in a major journal.

2. The big conclusion: They are unusually direct, writing that there is “credible evidence” that daily cannabis use is a contributory cause of psychosis.

3. The other disorders? The picture is less clear. They find evidence of an association with bipolar disorder (modest “with less consistent evidence”), depressive disorders (modest “in prospective studies”), and anxiety disorders (modest “with mixed findings”).

4. The literature is evolving, and there are many unanswered questions. On this, we can all agree: the bold claims of industry aren’t backed by the available evidence.

The full Lancet Psychiatry paper can be found here:

https://www.thelancet.com/journals/lanpsy/article/PIIS2215-0366(26)00086-6/fulltext

Selection 2: “Trends in the Prevalence and Severity of Alcohol and Cannabis Use Disorders Among US Adults”

Beth Han, Wilson M. Compton, Jennifer A. Hobin, et al.

JAMA Psychiatry, 22 September 2026

Although alcohol use disorder (AUD) remains a highly prevalent substance use disorder, the number of US adults with AUD declined from 28.8 million to 27.1 million from 2021 through 2024. By contrast, the number of adults with cannabis use disorder (CUD) increased from 15.3 million to 19.4 million from 2021 through 2024, paralleling increasing cannabis potency, expanding legalization, and decreasing perceived harm. To inform public health prevention and treatment strategies, we investigated patterns of changes in AUD and CUD prevalence and severity by age and sex, with particular attention to the growing divergence between these 2 substance use disorders.

So begins a brief report by Han et al.

Here’s what they did:

  • They conducted a cross-sectional study, drawing on data from the National Surveys on Drug Use and Health (NSDUH), which provided “nationally representative data on cannabis and alcohol use, CUD, and AUD….”
  • They included people over 18 years of age and used data from 2021 to 2024.
  • They performed logistic regression analyses to account for NSDUH’s “complex sample design and sampling weights.”

Here’s what they found:

  • There were 186 823 participants.
  • Demographics. Most were female (51.3%); many were aged 21-34 years (24.1%) or aged 35-49 years (24.5%).
  • Cannabis. Cannabis use disorder (CUD) increased substantially. Among men, past-year CUD rose from 7.3% in 2021 to 9.3% in 2024; among women, it increased from 4.5% to 5.6%.
  • Severity. Moderate-to-severe CUD also increased, from 3.1% to 4.1% among men and from 1.7% to 2.5% among women. The increases were particularly notable among men aged 35-49 and 50 years or older, and women aged 21-34, 35-49, and 50 years or older.
  • Alcohol. In contrast, alcohol use disorder (AUD) was stable or declining. (!) Overall AUD fell from 9.7% to 8.2% among women, while the change among men – from 13.3% to 12.6% – was not statistically significant. Among adults 21-34 years, both AUD and moderate-to-severe AUD declined in men.
  • Users. Among people who used cannabis, the proportion meeting criteria for CUD increased among men – from 32.9% to 36.2% – and the proportion of women with CUD who had moderate-to-severe illness increased from 37.0% to 45.0%. Among young adults with CUD, roughly half or more had moderate-to-severe CUD in 2024.

A few thoughts:

1. This is a good brief report, with a great dataset, and published in a solid journal.

2. The main findings in a sentence: They found divergent trends – cannabis-related problems are becoming more common and, in some groups, more severe, while alcohol-related problems are stable or declining.

3. To emphasize: it isn’t simply that cannabis use is increasing – it’s that the severity of cannabis use disorder is increasing, including among older adults.

4. The authors see clinical implications: “Findings repudiate conventional assumptions that cannabis carries a low addiction risk and that most young adults with CUD have mild symptoms.”

5. Like all studies, there are limitations. The authors note several, including some limitations of the dataset. “It may underestimate CUD and AUD prevalence and severity because NSDUH excluded unsheltered individuals and incarcerated populations.”

The full JAMA Psychiatry brief report can be found here:

https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2852558

Selection 3: “The Weed Got Too Strong”

Sivabalaji Kaliamurthy

The New York Times, 24 August 2026  

My patient was 14 years old the first time his grandmother drove him two hours to my clinic. He told me he tried weed when he was 8 and had been smoking or vaping it daily since he was 12, often using highly concentrated products purchased from friends or dealers. ‘It helps me relax,’ said the patient, who moved in with his grandmother after his mother died and his father was incarcerated.

His life told a different story. Now 16, this young man struggles with persistent depression, failing grades and escalating anger. He had punched holes in walls, been suspended from school and was hospitalized for suicidal thoughts. He’s one of many teens I treat whose use of highly potent cannabis has become a destructive force in their lives.

Americans have been using cannabis for generations, but today the drug is more available, more socially accepted and far more potent than ever.

So begins an essay by Dr. Kaliamurthy.

He notes that cannabis has changed. “Legalization and decriminalization have brought about rapid changes in the marketplace, and dispensaries around the country now sell plant buds alongside highly concentrated vape cartridges, gummies, edibles, waxes and beverages infused with the psychoactive compound THC. These newer products are specifically engineered to deliver THC in ways that are often more convenient and discreet than smoking cannabis. That shift is especially concerning for adolescents, whose brains are still developing and are more vulnerable to the effects of repeated exposure to high levels of THC.”

He observes the shift in potency. “A few decades ago, the typical cannabis plant contained 2 to 5 percent THC, and the more potent products averaged around 10 percent. Today’s cannabis bud products often contain 20 percent THC, while cartridges and concentrates can exceed 70 percent THC.”

He sees technology and market forces combining to change cannabis. “Advances in agricultural science allowed breeders to create cannabis strains with ever-higher THC concentrations. At the same time, innovations in vaping technology made these high-potency products without the smell or smoke of cannabis. Market forces accelerated this trend. Higher-potency products command higher prices and profit margins, creating strong financial incentives for the cannabis industry to push THC levels upward.” 

He speaks as a physician. “Doctors like me who treat children and adolescents are seeing more patients for cannabis-related reasons, including conditions such as cannabis use disorder and cannabinoid hyperemesis syndrome, which causes nausea, vomiting and severe stomach pain.” He argues that cannabis is different from other substances. “Unlike alcohol, which is rapidly cleared from the body, THC is stored in fatty tissues and released gradually over time. Adolescents who are using potent cannabis regularly have higher levels of THC in their bodies – a form of prolonged exposure not seen in previous generations.”

How to proceed? “We need a shift in how we regulate cannabis to account for the fact that it is not a uniform product.” He points to the success of tobacco control: “cigarette sales plummeted and the United States made big strides in public health. The same can be true one day for cannabis.” 

He makes recommendations:

  • Caps. “States should establish THC potency caps. Alcohol policy offers a useful parallel. Beer, wine and hard liquor are regulated and taxed differently based on strength. Cannabis should be treated similarly.”
  • Consistency. “Labeling and dosing must be standardized across states. Right now, some states require mental health warnings on cannabis products, but most do not, and there is no consistency in what information appears on the labels and how prominently it is displayed. Labeling should also include health warnings similar to those on tobacco products, informing consumers about the risk of dependence, the dangers of use during pregnancy, the risks of impaired driving and the heightened vulnerability of young people’s developing brains.”
  • Research. “We must invest in research. We need better data on thresholds for risk at the population level, as well as more prevention and treatment interventions for adolescents.”

A few thoughts:

1. This is a well-written essay on cannabis.

2. His point about the rise in potency of cannabis has been made by others. Still, it’s an important observation.

3. Whether you favour or oppose legalization, Dr. Kaliamurthy makes reasonable arguments, particularly about regulations.

The full New York Times essay can be found here:

https://www.nytimes.com/2026/08/24/opinion/weed-marijuna-children-regulation.html

Reading of the Week. Every week I pick articles and papers from the world of Psychiatry.