The popular drug fluoxetine, commonly sold under the name Prozac, has been detected in aquatic ecosystems worldwide, and now new research finds that Siamese fighting fish exposed to the drug become timid and weak, hurting their chances for survival.

The study, published in the Journal of Experimental Biology, shows how this and other drugs polluting the environment can impact wildlife.

“There has been growing concern over the past two decades regarding the prevalence of pharmaceuticals and personal care products in waterways worldwide,” lead author Teresa Dzieweczynski of the University of New England and her colleagues Brennah Campbell and Jessica Kane wrote.

Humans Accidentally Tame Flies, Fish, Others: Photos

The researchers say that many products, including fluoxetine, “are still in their active form when they enter sewage treatment systems, where they have limited removal because of their water solubility and resistance to biodegradation.”

The problem can therefore happen quite innocently, such as when a person on Prozac or certain other drugs goes to the bathroom and flushes. We trust that sewage treatment systems clean up our waste, but as the scientists point out, that cannot always happen due to the chemical nature of many drugs.

Since fluoxetine is common in some rivers where Siamese fighting fish live, Dzieweczynski and her team investigated how the drug can affect these fish, which are known for both their beauty and boldness.

Video: Flushed Fish Invading Oceans

The researchers compared the behavior of fish exposed to various amounts of fluoxetine to those that had no exposure to the drug.

The scientists wrote that “males exposed to fluoxetine were less bold and less consistent in their behavioral responses, and the correlations between boldness over time and across assays were weaker than those for unexposed males.”

This might at first sound like a good thing. After all, Prozac for humans has been hailed as a wonder drug since the mid 1980s. It is used to treat human psychiatric disorders such as depression and post-traumatic stress disorder. How the drug works has never been fully determined, but it is believed to increase levels of the neurotransmitter serotonin in the synapse between nerves by reducing reabsorption into nerve cells to relieve symptoms.

Top 10 Most Polluted Places on the Planet

For Siamese fighting fish, however, the drug-induced timidity could hurt the fish’s chances for survival.

“If exposure affects boldness, fitness may be decreased as individuals that fail to forage, avoid predators or attract mates will obviously have decreased fitness,” the researchers explained.

They continued, “Perhaps most importantly and alarmingly, the effects of exposure lasted even after fluoxetine was removed.”

The scientists call for additional studies on the chronic effects of the drug, not only to determine how best to protect wildlife from exposure to it, but also to determine more about how it impacts, in the long term, the people who are taking it.