None the Happier: Antidepressants in Water Make Fish Angry, Easy Prey

These days, millions of people are known to take anti-depression medication. But so do animals (by proxy), as tons of antidepressants leak into the water.

Fish are particularly adversely affected by anti-depression medications that leak into the water, a Swedish research has found. Among other things, fish tend to become more aggressive and stress-resistant, which makes them easy prey.

In Sweden alone, hundreds of thousands of patients take drugs for depression. Often they go straight through the body and leak into lakes and waterways after successfully passing through sewage systems and activated sludge units.

A group of Swedish researchers from Södertörn University examined the behavioral effects of antidepressant drugs on fish. According to project leader Martin Kellner, the pioneering research focused on selective serotonin reuptake inhibitors (SSRI) and used the three-spined stickleback as guinea pigs. These fish are common in the Northern Hemisphere and are known to live in fresh, brackish and salt water, especially in the Baltic Sea. Tests were also performed on zebrafish, which were also held in aquariums with low levels of the antidepressant drug citalopram for weeks.

In the course of the experiment, both fish species became less stress-sensitive, which in nature could spur a riskier kind of behavior, potentially increasing the dangers of being devoured by predatory fish. Furthermore, the fish also exhibited a loss of appetite, which can interfere with their reproductive capacity and ability to endure starvation periods.

Furthermore, fish embryos exposed to citalopram were later found to be more nervous, aggressive and made more lunges for food than other fish, Kellner noted.

“Generally, we used such exposure levels you could possibly find in nature outside an activated sludge unit. At the same time, we only examined one medication at a time. In reality, there is often a cocktail of many different drugs enhanced by other substances with various effects. It is difficult to say how fish in the natural environment are affected by this, it varies from waterway to waterway,” Martin Kellner said in a statement.