Salmon Are Being Exposed to Our Anti-Anxiety Medication, and It’s Making Them Take More Risks, Study Suggests Atlantic salmon exposed to a common anti-anxiety drug migrate faster, according to new research. That’s not necessarily a good thing Researchers Daniel Cerveny and Marcus Michelangeli collecting salmon from the Dal River in Sweden. Michael Bertram Humans take a lot of medication, and small doses of those drugs—including antibiotics, antidepressants, birth control and more—find their way in the environment through wastewater, even after it’s treated. Nearly 1,000 different pharmaceuticals have been detected in waterways all over the world, even in Antarctica. Now, a new study sheds light on how these drugs affect wildlife behavior. “Pharmaceutical pollution, or chemical pollution in general, is really this invisible agent of global change,” says Jack Brand, the study’s lead author and an environmental researcher at the Swedish University of Agricultural Sciences, to Benji Jones at Vox. “It’s probably posing a greater risk than at least what the public acknowledges. This is a potentially significant threat to our aquatic wildlife.” To better understand this risk, Brand and his team gave young Atlantic salmon the drug clobazam—a common anti-anxiety and sleep medication—in doses that might mirror what they’re exposed to in the wild. The team used tracking tags to monitor how the medication affected the fish’s 17-mile migration from the Dal River in Sweden to the Baltic Sea. The salmon that were given clobazam were more likely to reach the sea than the untreated fish. They also quickly passed through two major hydropower dams that often slow other fish down. The new findings were published in the journal Science last week. Scientists say the drugged salmon might have migrated differently because of an increased willingness to take risks. “It’s interesting to see how one problem impacts how they deal with another problem,” says Olivia Simmons, a salmon ecologist at the Norwegian Institute for Nature Research who was not involved in the study, to Rebecca Dzombak at the New York Times. “These bolder fish could just be going faster because they’re less inhibited.” But going faster isn’t necessarily a good thing for the salmon. “It’s important to realize that any change to the natural behavior and ecology of a species is expected to have broader negative consequences, both for that species and the surrounding wildlife community,” explains study co-author Marcus Michelangeli, a behavioral ecologist at Griffith University in Australia, in a statement. Brand tells Jonathan Lambert at NPR that the fish exposed to clobazam may be more risk-prone and solitary, “and therefore just sort of beelining it through the dams rather than waiting around for their salmon friends.” A dam in Älvkarleby, Sweden, which is one of the obstacles that salmon in the Dal River must navigate on their migration. Rebecca Forsberg The researchers also took their study into the lab to better understand the impact of the drugs on the salmon, and the fish displayed other signs of solitary behavior. Clobazam appeared to change the way the fish interact with each other, making them less likely to school in groups—even when a predatory northern pike swam nearby. That independence could make them more vulnerable to being eaten. “It’s like playing poker,” adds Giovanni Polverino, a behavioral ecologist at the University of Tuscia in Italy who was not involved in the study, to the New York Times. “The more risks you take, the more chances you have to lose everything,” he adds. “In this case, the fish’s life.” Still, there’s hope on the horizon for the world’s fish, Michelangeli notes in the statement. Wastewater treatment options are getting better at reducing pharmaceutical contamination, and researchers are also working on making drugs that degrade more quickly. “By designing drugs that break down more rapidly or become less harmful after use, we can significantly mitigate the environmental impact of pharmaceutical pollution in the future,” he says. Get the latest stories in your inbox every weekday.