Popular anti-depressant Prozac might be easing the pain of depression for humans, but apparently it's turning fish into crazed homicidal maniacs: according to a new study, fish are eating traces of the drug found in wastewater, and they're becoming more aggressive, anxious, anti-social and in some cases, driven to kill each other. Elizabeth Wurtzel did not predict this.

The yet unpublished study [pdf] was conducted by researchers at the University of Wisconsin-Milwaukee; they found that male fathead minnows who swim in water tainted with low-to-middling concentrations of Prozac experience serious brain and behavioral shifts, making them spend more time alone in their nests, more anxious of the threat of predators, less willing to reproduce with females and even led some of them to kill females.

And, no, these fish weren't prescribed antidepressants by a licensed psychiatrist. They were exposed to traces of the drugs in wastewater, a small percentage of which get flushed out in the urine of humans who take them. "The fish downstream of the wastewater treatment had elevated concentrations of two antidepressants … Zoloft and Prozac," Edward Furlong, a research chemist at the U.S. Geological Survey based in Boulder, Colorado, told Scientific American. "And these were relatively low in water compared to others." Other fish, like rainbow trout, experienced antidepressant-driven brain shifts as well.

Researchers are concerned that pharmaceuticals could have bigger environmental implications, and perhaps harm human brains, too. In 2008, a survey of drinking waterways in the United States found traces of drugs in 53 out of 74 waterways tested. "It's not just an environmental question but a human question as well," Rebecca Klapper, the lead researcher on the study, told ABC News. And according to WebMD, side-effects of Prozac in humans are similar to the ones found in the fish, if to a lesser extent: the site lists side-effects like unusual or severe mental/mood changes agitation, unusual high energy/excitement and decreased interest in sex.