Fish Exposed to Prozac Exhibit Significantly Altered Behavior


Concentrations of Prozac as low as 1 microgram per liter (μg/L), a concentration that has been found in many freshwater environments, were found to significantly impact the mating behavior of fathead minnows, specifically nest building and defending. Males were also found to display aggression, isolation, and repetitive behaviors at higher concentrations. Predator avoidance behaviors in males and females were also impacted at 1 μg/L. Feeding was impacted at 10 μg/L and in the highest exposure (100 μg/L), egg production was limited by deaths of females due to significant male aggressive behaviors in the first two weeks of exposure. “With increased aggression, in the highest level of concentration, female survivorship was only 33% compared to the other exposures that had a survivorship of 77–87.5%. The females that died had visible bruising and tissue damage,” according to c0-author Rebecca Klaper.

Weinberger, J., Klaper, R.; Environmental concentrations of the selective serotonin reuptake inhibitor fluoxetine impact specific behaviors involved in reproduction, feeding and predator avoidance in the fish Pimephales promelas (fathead minnow). Aquatic Toxicology. June 2014 151, 77–83 DOI:10.1016/j.aquatox.2013.10.012

See also;
Fish exposed to antidepressants exhibit altered behavioral changes (Science Daily)
Fish exposed to antidepressants exhibit altered behavioral changes (

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Kermit Cole
Kermit Cole, MFT, founding editor of Mad in America, works in Santa Fe, New Mexico as a couples and family therapist. Inspired by Open Dialogue, he works as part of a team and consults with couples and families that have members identified as patients. His work in residential treatment — largely with severely traumatized and/or "psychotic" clients — led to an appreciation of the power and beauty of systemic philosophy and practice, as the alternative to the prevailing focus on individual pathology. A former film-maker, he has undergraduate and master's degrees in psychology from Harvard University, as well as an MFT degree from the Council for Relationships in Philadelphia. He is a doctoral candidate with the Taos Institute and the Free University of Brussels. You can reach him at [email protected].


  1. 1μg/L isn’t all that small a concentration, no wonder it can influence the water animals. The calamity is that it actually is present in the environment in such amounts. Same goes with sex hormones unfortunately :(.

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  2. One more thought: anyone saw a study on how psych drugs affect SOCIAL behaviour in mice or other mammals? The studies are usually done with fear and helplessness-related paradigms which are done on rodents in isolation but I can’t remember one paper that would look on the social aspect…

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    • That’s why I’d love to see the experiment on mice with social behaviour. The primary tests for psych drugs are done using a battery of standard assays which are done on a single individual at a time. Everyone with half a brain in the field will know are very simplified tests for fear and activity levels, no more, no less. People talk about depression models etc. but the fact of the matter is the only model for depression is a human because we can’t ask a mouse how it feels. We can observe behaviour but the reasons for the same behaviour may be completely different with different drugs. That being said, there are also some assays for social dominance and aggression in mice that seem more informative but I’ve never seen one used to access the effect of drugs. I actually want to speak to a friend now who’s doing some of these thing if they ever thought of that, sounds like a good idea.

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      • Here’s an interesting study that challenged addiction studies on rats. Rats were put into interesting environments with other rats and did not live for cocaine.

        How these drugs impact animals in the environment is a little scary.

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