Researchers at Umea University exposed wild European perch to water with different concentrations of Oxazepam, a common psychiatric medication, The New York Times reported Friday.
The drug can make its way into waterways after being flushed, excreted or discarded, the researchers said.
Fish exposed in the study to dilute concentrations of the drug showed a tendency to be less social, to be more active and to eat faster, the researchers said, all of which could create ecosystem impacts.
Donald Tillitt, a toxicologist with the U.S. Geological Survey, who was not involved in the research said the study is environmentally "relevant."
He said the measures of fish behavior examined in the study "are all important ones that we like to look at when we're trying to see the environmental effects of pharmaceuticals."
"It seems to be a solid study with an environmentally relevant species," he said.