Anti-Anxiety Medications Ending Up in Our Water

Written by on February 17, 2013 in Marine Life, Physical Oceanography
European perch (Perca fluviatilis).

European perch (Perca fluviatilis). Photo credit: Dgp.martin.

Researchers have recently found that residue from anti-anxiety medications in waterways is affecting fish behavior.

The medication is called oxazepam and belongs to the most widely prescribed class of anti-anxiety drugs, benzodiazepines. It ends up in the water after it is passed through an individual to their urine and turns a normally timid fish into a bold, anti-social and voracious one.

“This study really highlights the importance of non-lethal effects,” said Todd Royer, an ecologist at Indiana University. Even if toxins aren’t killing fish, they can still dramatically alter ecosystems.

By measuring concentrations of oxazepam in the Fyris River in Sweden, the researchers found that one particular species of perch (Perca fluviatilis) had accumulated the drug in concentrations at least six times higher than in the surrounding water.

To test the affect the drug has on these fish, the researchers exposed juvenile perch to two different concentrations. One group was exposed to concentrations twice what the fish in the Fyris river were and the other was exposed to concentrations nearly 1,000 times higher.

The researchers found that even when exposed to lower concentrations, the fish still exhibited altered behavior. Instead of swimming toward other perch, as they would normally, the medicated fish became anti-social and turned away from other fish. In addition, perch typically like to stay in familiar territory, but the medicated perch became more aggressive, exploring unknown areas of the tank. They were also quicker to eat the food in their tank.

The researchers believe this is because the drug caused the fish to be less inhibited by fear, which could ultimately affect their survival in the wild.

“Anti-anxiety drugs are viewed as calming and soothing, but in fish it was the opposite,” said Micael Jonsson, an ecologist at Umeå University and a co-author of the study. “If the fish were anxious to begin with, perhaps the drug reduces anxiety and allows the fish to become more active.”

This isn’t the only drug that ends up in the water–many contraceptive pills and some other drugs can also affect fish behavior. Solving this problem, however, is not going to be easy. Removing the chemicals before they reach rivers would be expensive and, according to Charles Tyler, an ecotoxicologist at the University of Exeter, would carry a high carbon footprint.

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Copyright © 2013 by Marine Science Today, a publication of Marine Science Today LLC.

About the Author

About the Author: Emily Tripp is the Publisher and Editor of She holds marine science and biology degrees from the University of Miami's Rosenstiel School of Marine and Atmospheric Science and a Master of Advanced Studies degree in Marine Biodiversity and Conservation from Scripps Institution of Oceanography. When she's not writing about marine science, she's probably running around outside or playing with her dog. .


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  1. Matt R says:

    I should be more upset about this issue but after eating sushi last night… I guess it’s hard to get upset when you’re full of anti-depressant sashimi rolls