While the recreational use of marijuana is usually associated with a more peaceful mental state, scientists just a made a surprising discovery.
As detailed in a meta analysis of cannabis-related studies published last month in the journal Psychological Medicine, a team of scientists in the UK discovered a significant link between cannabis use and an “increased risk of violence.”
The headline finding was that they found cannabis users were statistically more likely to be the perpetrators of violent acts. They also found that the use of the drug — particularly among women and mixed-gender cohorts — was “significantly associated with an increased risk of becoming a victim of violence” as well.
While it’s a classic case of correlation, not causation — the researchers stop far short of suggesting the drug directly motivates users to be more violent as we’re far from reaching a scientific consensus on the matter — the findings “underscore the importance of addressing this issue at both a societal and clinical level,” according to the paper.
In other words, it’s a highly nuanced and complex relationship with plenty of other factors at play.
“As a clinician, I’ve seen how heavy cannabis use can be a factor in violence,” said coauthor and King’s College London professor Marta Di Forti in a statement. “We’ve been cautious for a long time about how far we could go in describing this link, but a review of this size lets us speak with more confidence about the risks, while being careful not to stigmatise people who use cannabis more broadly.”
“As cannabis becomes more commercialized and legalised around the world, the conversation about its risks has focused mostly on the person using it,” added coauthor and King’s College London professor of psychiatric research Sir Robin Murray. “This review shows that violence, both committing it and experiencing it, needs to be part of that conversation too.”
For their paper, the researchers examined 63 cannabis-related studies, involving just over 265,000 subjects.
The researchers found that cannabis users “may place themselves in risky situations,” which could help explain the “increased vulnerability” to violence. Users may also be exposed to “peers who engage in substance use or criminal activities.”
The risk of violence was also more pronounced among psychiatric patients. Previous resarch has found that people who already suffer from pre-existing mental conditions such as psychosis may experience “poorer clinical outcomes” through continued cannabis use.
“Given the higher rate of cannabis use among individuals with severe mental disorders compared to the general population, this group represents a particularly at-risk population in terms of violent behavior,” the paper reads.
The researchers offered some key takeaways from their findings. At the societal level, the researchers suggest that “violence should be considered alongside other established cannabis-related harms when developing prevention strategies, public education campaigns, and regulatory policies.”
At the clinical level, the research highlights the “necessity for mental health professionals to routinely assess cannabis use in individuals presenting with violent tendencies, particularly among those with severe mental illness.”
However, to get a better picture of how cannabis use relates to violence, future studies will need to “disentangle causal pathways” by diving into how, why, and when people use the drug in more detail. Other studies should also “examine whether reducing cannabis use through clinical or public health interventions leads to reductions in violent behavior,” the researchers conclude.
Each year, about this time, the Karolinska Institute and Royal Swedish Academy of Sciences — both in Stockholm, Sweden — announce three world-changing achievements. People who pioneered the work in these fields will receive the most coveted science awards on Earth: the Nobels.
The first of the 2026 prizes was awarded for finding a light switch for the brain. The second goes for developing a literally super-cool way to study elusive particles bombarding Earth from outside our solar system. And the last prize highlights the importance of being able to preferentially make certain “handed” molecules.
All three achievements opened up major new windows on — and opportunities in — biology, physics and chemistry.
Let’s start with the human brain. It hosts nearly 90 billion neurons. They talk amongst each other through some 100 trillion connections. This brain chatter allows our minds to learn, adapt and interact with the world around us.
The 2026 Nobel Prize in physiology or medicine went to Karl Deisseroth, Peter Hegemann and Georg Nagel for developing ways to control nerve cells with light. The technique, called optogenetics, opened new ways to study the brain by turning individual neurons on and off. #nobel#optogenetics#sciencenewsNikk Ogasa Getty Images/Alexander Pytskiy/JONATHAN NACKSTRAND/JOHN SAEKI,LAURENCE CHU/VALENTINA BRESCHI,JONATHAN WALTER,SYLVIE HUSSON,OLIVIER THIBAULT
To find out how, brain scientists needed a special tool. They long “dreamed” of something that might let them “turn specific neurons on or off with great precision,” notes Abdel El Manira. He spoke on Oct. 5, describing the prize for this tool.
The path to the prize started in an unlikely place: the “eye spot” of a single-celled green alga.
In the early 2000s, biophysicists in Germany discovered a unique protein in that alga’s “eye” spot. The two researchers were Peter Hegemann (who now works at Humboldt University in Berlin, Germany) and Georg Nagel (at the Julius-Maximilians-Universität Würzburg in Germany). The protein that caught their interest had a long name: channelrhodopsin (CHAA-nel-roh-DOP-sin).
When light hits it, the protein produces an electrical impulse. This triggered the alga to move. Later research would show light caused that protein to open like a pore. That let positively charged ions flow into the cell. They are what caused the electrical impulse.
Hegemann and Nagel “had just discovered the switch neuroscientists had long dreamed of,” says El Manira.
Building on the that work, Karl Deisseroth tried using that protein to see if it could turn on brain cells. A neuroscientist, he works at Stanford University in California.
He was part of a team that inserted the gene to make channelrhodopsin into rat nerve cells. These were growing in dishes in the lab. Shining light on the cells triggered an immediate reaction.
This team also put the gene into nerve cells within the brains of living mice. The researchers inserted optical fibers at the same spots, right through the rodents’ skulls. By shining blue light through the fibers, the researchers could now control the movements of the rodents’ whiskers.
Researchers later went on to test the links between other brain circuits and behaviors.
In short order, optogenetics “transformed neuroscience,” El Manira says. It offered a window on the workings of healthy brains, he says. It helped show how brain circuits can be disrupted, too, he adds. Those findings, he notes, could help researchers treat conditions such as blindness, depression and dementia.
In fact, we didn’t have to wait long for news in one of those areas. Just two days after this Nobel was announced, other researchers described a light therapy for retinitis pigmentosa (Reh-tih-NY-tis Pig-men-TOW-sah). This blinding disease slowly kills off light-sensing cells in the eye’s retina. Optogenetics, the new report showed, helped improve light sensitivity in seven of 10 treated people.
Neutrinos have no electric charge. They can pass through objects without interacting. In fact, billions of these ghostly particles pass through each of us every second.
Fusion reactions in our sun form most of them. But some had been thought to come from much farther away — in high-energy particle collisions too far off to observe.
Detecting such neutrinos from well beyond our solar system had long been a goal of scientists. Because neutrinos are not deflected by magnetic fields and rarely interact with matter, detecting their path could point back to their distant source. Scientists hoped to one day figure out where and how the universe accelerated these super-small particles to super-high energies.
In the 1980s, physicist Francis Halzen of the University of Wisconsin–Madison had an insight: The South Pole should be an ideal place to look for the flashes of light created by the rare events when neutrinos collide with atomic nuclei. Ice deep within the Antarctic ice sheet could make a large, dark, transparent stage for such a neutrino light show.
Francis Halzen has won the 2026 Nobel Prize in physics for his vision and scientific leadership of the IceCube Neutrino Observatory. IceCube gave us an entirely new way to see the universe. #nobelprize#physics#sciencenews Nikk Ogasa Getty Images/MARCO BERTORELLO/NSF/Martin Wolf & Sven Lidstrom, IceCube
In part, Halzen got this year’s physics Nobel “for his decisive contributions to [IceCube].” notes physicist Mark Pearce. But Halzen also won for “the discovery of high-energy neutrinos of astrophysical origin,” he adds. Pearce, who chairs the Nobel committee for physics, spoke during the Oct. 6 award announcement by the Royal Swedish Academy of Sciences.
IceCube had been a gamble. “Nobody knew whether a kilometer-field detector was actually large enough to discover neutrinos beyond our atmosphere from the universe,” Halzen said in a phone call during the announcement ceremony.
In fact, he noted, “It only took us two years to detect them.”
This year isn’t the first time a Nobel has gone for work on neutrinos. Two physicists received the prize in 2015 for demonstrating that neutrinos have mass.
In nature, the building blocks of life exhibit a striking pattern. Many can exist in two mirror-image structures, much like your right and left hand. Such molecules are said to be chiral (KY-rul). However, in nature, such chiral molecules overwhelmingly occur in just one form. Amino acids, for instance, are nearly always left-handed.
Known as homochirality, this dominance of one type of handedness had long puzzled scientists.
When chemists first attempted to make chiral molecules in the lab, they ended up with roughly 50-50 mixes of right- and left-handed molecules. Why?
“It is this puzzle that this year’s laureates have solved,” said Heiner Linke. He spoke during the Oct. 7 announcement of the chemistry prize by the Royal Swedish Academy of Sciences.
Two scientists will split this Nobel prize. Henri Kagan works at the Université Paris-Saclay in France. Kenso Soai works at Tokyo University of Science in Japan.
Henri Kagan and Kenso Soai won the 2026 Nobel Prize in chemistry for their work on controlling the production of mirror-image molecules. Their discoveries have helped pharmaceutical companies develop safer drugs. #nobel#chemistry#sciencenews Nikk Ogasa Getty Images/Evening Standard/Paul Fievez/Keystone/JONATHAN NACKSTRAND
The award winners’ research has greatly aided development of medicines. A lot of active drug molecules are chiral. But while one form may have a medicinal effect, its mirror-image form might have no effect — or worse, be harmful.
Consider thalidomide (Thuh-LID-oh-myde). Thousands of babies were born in the 1950s with severe birth defects. Their mothers had been prescribed thalidomide while they were pregnant to treat anxiety and nausea. Science would later show that the left-handed form of the drug was toxic. (Even taking the “safe,” right-handed form wouldn’t solve the problem. In the body, it could morph into the left-handed form.)
In 1986, Kagan’s team was the first to report chemical reactions that would lead to production techniques that helped solve the problem. These could make a far larger than normal share of left- or right-handed forms.
Several years later, Soai and his colleagues reported that they had figured out how to make a chiral catalyst that could, in turn, be used to form itself. That allowed his team to perform reactions that resulted in products made almost entirely of one “handed” form of a chiral molecule.
“This is not the final answer,” Soai said of this work. He had called in from Japan to the Nobel announcement ceremony. Speaking to future generations, Soai said, “the study of chirality should be more and more developed.”
The new Nobel scientists will each get a medal. The winners in each category will also split 12 million Swedish kroner (roughly $1.2 million).
For about a decade, the mainstream understanding has been that psychedelics cause chaos in the brain. Brain networks—the stable patterns of communication that handle vision, attention, or our sense of self, and more—loosen and start talking to each other all at once. EEG traces get noisier and more complex. “Think of the networks of the brain as highways,” says Devon Stoliker, a neuroscientist at Monash University. “Under psychedelics, these highways break down into many different directions.”
In a recent Nature study, Stoliker’s team designed an experiment to test whether these directions are truly chaotic and random. Researchers gathered 62 people who had never taken a psychedelic before, gave them 19 milligrams of psilocybin, a common psychedelic found in certain fungi, and scanned their brains. Then, they used AI to analyze the drugged and sober brain scans. What emerged was not exactly chaos.
An uninterrupted trip
Stoliker thinks chaos is not a satisfactory explanation for psychedelics’ effect on the brain. “It never really explained why an individual would have a meaningful experience, why they might have insight, why they might experience clarity, and why these might translate into positive psychological changes,” Stoliker says. To investigate if there are other explanations, he and his colleagues designed a study called PsiConnect.
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