Mood-boosting drugs make unhappy fish

Scientists recently did experiments on several species of freshwater fish to see how they reacted to antidepressants in their water. Normally a bottom-dwelling species, this bass exposed to antidepressants started swimming at the surface, partially out of

Clemson University’s Institute of Environmental Toxicology

When you’re sick, you might take medications to help you fight off infection, lower a fever or clear a stuffy nose. But once those drugs leave your body, chances are they will find their way into nearby lakes, ponds, rivers and streams.

Drugs end up in a body of water because you excrete them in urine. When you flush a toilet, the wastewater travels to a treatment plant. There, bacteria and other material are filtered out and the cleaned water is returned to natural bodies of water. The trouble is, wastewater treatment plants don’t filter out drugs. Some people even flush unused drugs down the toilet, only adding to the problem.

While medications are meant to help a person feel better, they’re not good for wildlife. Over the past several years, scientists have begun to test how common drugs are in freshwater ecosystems. Researchers also are starting to learn more about how medications meant for humans affect the animals that accidentally ingest the drugs.

Recently, several scientists tested how a group of drugs called antidepressants affects freshwater fish. For many people with an illness called depression, antidepressants can be lifesavers. People with depression may feel sad or anxious for extremely long periods of time, lose interest in activities they once enjoyed and have difficulty sleeping or concentrating. Antidepressants help improve these symptoms for some people.

Several years ago, researchers discovered that some species of fish living near wastewater treatment plants had antidepressants in their brains. “Pretty much any water sample in the vicinity of a wastewater treatment plant will test positive for some group of antidepressants,” says chemist Melissa Schultz, of the College of Wooster in Ohio. This finding inspired a number of scientists to learn how these drugs affect fish and other wildlife.

In their experiments, researchers exposed species of fish in a laboratory to different brands of antidepressants. Then, the scientists tested the fishes’ responses to a number of things, such as the cues predators make or the appearance of prey animals.

Some hybrid striped bass exposed to the antidepressant Prozac eventually began hanging vertically in the water — a highly unlikely pose — and stopped eating.

Clemson University’s Institute of Environmental Toxicology

The researchers found that antidepressants affect fish species in numerous ways, from diminishing their response to predators to slowing down their prey-hunting techniques. One unexpected result even showed that a type of antidepressant called fluoxetine acts like estrogen, a primarily female hormone, when in the bodies of adult male fathead minnows.

Fluoxetine, sold under the brand name Prozac, caused these male minnows to produce an egg protein normally made only by females. In addition, males exposed to fluoxetine did not make the bright colors and facial bumps usually used to attract mates. More testing needs to be done to determine whether these changes affect minnows’ ability to mate.

It’s important to keep in mind that in any lake or stream, fish and other organisms aren’t just exposed to antidepressants, Schultz says. Antibiotics, anti-inflammatories, and even caffeine all make their way through water treatment plants and back into the environment. What happens to fish and other animals when they’re exposed to all of these drugs in combination? For now, nobody knows, Schultz says – leaving the door open to many future research questions.

This video shows a hybrid striped bass quickly gobbling up four minnows. Fed only once every three days, the bass tend to become quite aggressive about downing their meals. After being exposed to high concentrations of Prozac, however, some bass took up to two minutes to capture their first minnow and didn’t finish all four with the allotted 25 minutes. Over the nearly month-long experiment, a few bass lost their appetites altogether.