Psychiatric drugs taken by humans to
cope with anxiety are being excreted and flushed into waterways where they are
probably affecting fish behaviour.

This is the conclusion of a new Swedish study reported in Science
magazine.

The Umea University-led investigation exposed laboratory perch to the drug
Oxazepam at levels equivalent to the residues found in rivers and streams.

The fish were found to eat faster, to be less social and to be bolder than
animals that were not dosed.

Umea’s Tomas Brodin said the behavioural changes seen in their lab animals could have unexpected evolutionary and ecological consequences if reflected in wild populations.

“The strong behavioural modifications we saw were at low concentrations, and
I firmly believe we could go even lower and still see these effects,” the
researcher told BBC News.

“We looked at just one benzodiazepine-type drug but there are many others out
there, and they probably all have the same effects on fish and other
vertebrates. So we may be underestimating what is happening in nature.”

Dr Brodin was speaking here in Boston at the annual meeting of the American
Association for the Advancement of Science (AAAS). His address was timed to
coincide with the journal publication.

The fish in the Umea study were measured to have concentrations of the drug
in their muscle tissues that were comparable to those found in wild animals.