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Government must end unethical and exploitative forced swim test


3 min read

Imagine this terrifying scenario: Without warning, you are tossed into a deep tank of water. Frantically paddling and clawing at the sides, you look for any possible escape route. But it’s a futile effort.

Soon you start to float, modifying your behaviour in order to conserve energy as you try to keep your head above water and evade death. Your efforts are in vain because you’re eventually going to be killed anyway – by gassing, blunt force trauma to the head, an overdose of anaesthetic or having your neck broken. This nightmare is a reality for thousands of animals.

The Home Office is currently reviewing its policy on the sadistic forced swim tests. But considering both the science and suffering, there should be only one logical policy revision: they must end.

Forced swim tests are a completely unreliable measurement of human depression and other mental health conditions

In these experiments, mice, rats and other rodents are placed into inescapable cylinders of water. Experimenters then observe the animals’ behaviour. Lab workers conducting these tests claim the experiments offer information that’s applicable to human depression and other mental health conditions. For example, animals who float faster and spend more time floating purportedly demonstrate “behavioural despair”, which is supposedly an indicator of depression-like symptoms. This assertion is made despite arguments that floating is actually an adaptive behaviour necessary for survival and the animal is simply trying to conserve energy.

Sometimes rodents are dosed with test antidepressant compounds prior to the experiment in an attempt to find new treatments for humans. However, analysis of publicly available data of over 100 compounds from 15 major pharmaceutical companies revealed that the test can’t reliably predict whether those same compounds have any effect in humans. GlaxoSmithKline, AstraZeneca, Pfizer and other big pharmaceutical companies see no value in these tests and don’t use them. More than a dozen top UK universities have also shunned the archaic experiments. Newcastle University said the test was “outdated and ethically unacceptable” and that the school “cannot foresee any research where this test would be proposed or could be scientifically or ethically justified”.

Forced swim tests are a completely unreliable measurement of human depression and other mental health conditions. There are considerable neurobiological differences between human beings and rodents. Humans and mice are different! Using these worthless tests in an attempt to study human illness is a disservice to those suffering from real, debilitating mental health conditions.

A Home Office–initiated publication on the forced swim test reported the absence of compelling data that might link its results to anything relevant or translatable to humans. In fact, in the same publication, which included experts from the Medicines and Healthcare products Regulatory Agency, suggested that these irrelevant experiments could even hinder the development of effective new antidepressants for humans.

The scientific literature is replete with examples in which several classes of existing antidepressant drugs didn’t produce the expected result in the forced swim test. Even in the product monograph for Prozac, the best-known antidepressant on the market, the manufacturer states that the drug “does not reduce immobility in the forced swimming test in rats”.

Forced swim tests aren’t a regulatory requirement for new antidepressants. Although there are innovative animal-free approaches to research in this area, a “replacement” wouldn’t be required – per policy – in order to end these unnecessary, exploitative tests. The Home Office could simply remove forced swim tests from future project applications and end its unethical use for good. It would be good science and it would make good sense.

As the Home Office reviews its policy on the forced swim test, I urge everyone to sign the petition urging Home Secretary Suella Braverman to end all use of this test in the UK.


Rachael Maskell, Labour MP for York Central

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