Antidepressants meant to treat humans can also affect aquatic animals when those drugs enter waterways.

In a paper published today in the journal Ecosphere, researchers found that crayfish exposed to moderate levels of the antidepressant citalopram, commonly sold as Celexa, spent significantly more time foraging for food and less time in hiding. The behavior could make the crayfish more vulnerable to predators, and their altered behavior could, over time, have other effects on stream ecosystems.

The study was performed in a research center in a waterway that mimicked the natural environment, and crayfish were exposed to drug levels found in real-world settings.

“It was surprising to see the extent to which the behavior changed,” says study co-author