Today in Science: The link between cannabis and psychosis in teens is real

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May 5, 2025—The amazing globe-trotting painted lady; why pot use can lead to psychotic disorders in teens; and poetry plays a key role in dolphin research. —Andrea Gawrylewski, Chief Newsletter Editor TODAY'S NEWS Yangtze finless porpoise. Wenpu Wang/Getty Images Researchers used mentions of the critically endangered Yangtze finless porpoise in ancient Chinese poetry to document the species' distribution over the last 1,400 years. | 2 min read New rules for self-driving cars announced last month lessen crash reporting requirements and widen testing access for U.S. robotaxis. | 4 min read Tense conversations often end with "let's agree to disagree." But that might cause more harm than good, says a communications expert. Here's what to do instead. | 5 min read Most clicked yesterday: National Science Foundation Halts Funding Indefinitely. | 3 min read More News TOP STORIES Jim Mayes/Getty Images Painted Lady Fliers Ecologists captured 40 painted lady butterflies and determined where the creatures were born based on the isotopes of hydrogen and strontium in their wings. The results showed that individual butterflies can fly up to 2,500 miles from Europe to overwintering grounds in the African Sahel, journeying over the Mediterranean Sea and the Sahara Desert on the way. A few even inadvertently cross the Atlantic Ocean to South America, other researchers have found.   How they do this: Painted ladies are quite well-suited to long-distance travel. They weigh less than a gram but their triangular forewings propel them at up to 30 miles per hour at high altitudes. Their yellow fat reserves keep them going, plus they can shiver if they get cold. Many different varieties of plants are appealing to them, so they can feed wherever they venture.   What the experts say: Hundreds, if not thousands, of insect species most likely migrate huge distances, including dragonflies that cross the Indian Ocean, moths that traverse Australia and plant hoppers that windsurf through East Asia. But most of these journeys are undocumented, says University of Ottawa ecologist Megan S. Reich. "There are some incredible insect migrations." Pot Linked to Psychosis in Teens Researchers tracked the onset of chronic psychotic disorders among more than 11,000 teenagers in Canada over several years. By the time the cohort reached age 20, the cumulative incidence of psychotic disorders was about 4 percent in those who had used cannabis in the past year compared with less than 1 percent of nonusers.   Why this matters: New strains of cannabis are highly potent, making them more addictive and potentially more dangerous, especially to teenagers, writes Carrie E. Bearden, a professor of psychiatry and biobehavioral sciences and psychology at UCLA. The risk of psychosis increases with higher levels of delta-9-tetrahydrocannabinol (THC), the intoxicating component of the cannabis plant.    What the experts say: Why are teens particularly affected? The same molecules in the brain that interact with THC (known as the endocannabinoid system) play an essential role in brain development. "There is growing evidence from both animal and human studies that early cannabis exposure can disrupt the way brain cells, or neurons, respond to what we experience, and how they talk to each other to make those experiences memories," Bearden says. André J. McDonald, modified and restyled by Ripley Cleghorn; Source: "Age-Dependent Association of Cannabis Use with Risk of Psychotic Disorder," in Psychological Medicine, Vol. 54, No. 11; August 2024 Want to dive deeper into the science that interests you? Consider a subscription to Scientific American. Today in Science readers get special discounts! EXPERT PERSPECTIVES At least five medical research journals have received letters from the federal government accusing them of bias and demanding that they accept "competing viewpoints" in their editorial processes. Not only do these letters make clear that government officials know shockingly little about how research journals work, but they represent "part of a calculated strategy to identify, isolate and intimidate researchers who, and institutions that, acknowledge realities like inequality, social differences and structural violence," writes Eric Reinhart, a political anthropologist, social psychiatrist and psychoanalytic clinician. | 5 min read More Opinion

Butterfly populations are in decline around the world, with some species experiencing 90 percent loss of their numbers. Habitat destruction, insecticide use, rising temperatures and drying landscapes can all harm these insects. What can you and I do? Let grasses grow long in your yard (unless you're governed by a strict H.O.A.) and plant native flowers that butterflies love. Thanks for exploring this scientific world with me. You can always send your thoughts and feedback to: newsletters@sciam.com. Today in Science returns tomorrow.    —Andrea Gawrylewski, Chief Newsletter Editor

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