Anxiety takes a toll on people: they worry, they feel irritable, they avoid social gatherings—like that upcoming New Year’s Eve party. Juvenile salmon also experience stress when faced with unfamiliar situations, such as migrating out to sea where they’ll encounter predators. While anti-anxiety medication helps countless humans function better in their daily lives, new research shows the drugs also make salmon less inhibited, which can have potentially devastating effects.

In a study out of Sweden’s Umeå University, researchers show oxazepam—a pharmaceutical prescribed to humans for the treatment of anxiety, alcohol withdrawal, and insomnia—affects the downstream migratory behavior of Atlantic salmon. Exposing fish to anti-anxiety medication isn’t something that only happens in scientific studies: when humans excrete drugs, some can end up in wastewater effluent and subsequently in sensitive habitats where salmon may get an unintended dose. The researchers found that when fish ingest oxazepam, it makes them migrate faster and farther—potentially recklessly so.

Leaving the freshwater nursery and heading out to sea is part of the salmon lifecycle, but landing in the big blue too soon can be risky. Fish may find ocean conditions unfavorable—too cold, too dangerous, or lacking food, for example.

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