Antidepressants being taken by humans to combat depression, are finding their way into the brains of wild fish through waterways and malfunctioning sewage plants, according to new research.
Scientists have found that ten species of fish living in the Great Lakes region of North America, had high concentrations of Zoloft, Celexa, Prozac, Sarafem lodged in their brains when they were caught.
Although the researchers reassured people that these fish (which included bass and walleye), would not pose a danger if they were eaten, they emphasised that we should be “very concerned” about the threat it poses to biodiversity.
The percentage of Americans taking antidepressants has risen 65% between 1999-2002 and then 2011-14, according to the National Center for Health Statistics, and there has been a similar pattern in the UK where antidepressant prescriptions doubled in a decade.
In 2015, there were 61 million antidepressant items prescribed to NHS patients in Britain, which was 31.6 million (107.6%) more than in 2005 and 3.9 million (6.8%) more than in 2014.
Lead scientist Diana Aga, at Buffalo College of Arts and Sciences, said: “Fish are receiving this cocktail of drugs 24 hours a day, and we are now finding these drugs in their brains.”
Concentrations of the drugs were building up over a period of time, meaning that in some cases the levels of antidepressants found in the fish’s organs were 20 times higher than in the river water itself.
The highest concentration of a single compound was found in a rock bass, which had about 400 nanograms of norsertraline—a metabolite of sertraline, the active ingredient in Zoloft—per gram of brain tissue.
Caught in the Niagara River, which connects Lake Erie and Lake Ontario, via Niagara Falls, scientists were trying to understand not just how extensive this problem is, but whether these drugs were affecting fish behaviour too.
“We didn’t look at behaviour in our study, but other research teams have shown that antidepressants can affect the feeding behaviour of fish or their survival instincts.
“Some fish won’t acknowledge the presence of predators as much,” said Aga.
It also seems to be creating “suicidal shrimp” that swim towards light instead of away from it, which obviously creates a problem for that species population.
Randolph Singh, who worked on the study, said: “The risk that the drugs pose to biodiversity is real, and scientists are just beginning to understand what the consequences might be.”
Aga explained that fixing outdated sewage treatment plants would help reduce the scale of the current problem.
It is not yet known whether different drugs have a different impact on the fish, or are absorbed to differing degrees - the only antidepressant found in this study that is also prescribed on the NHS is Prozac.
They also prescribe Cipramil, Priligy, Cipralex, Seroxat, Lustral and Faverin.