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University of Edinburgh called upon to stop ‘behavioural despair tests’ on mice

ByBill Hodgkinson

Jan 27, 2021

CW: depression, suicide

The Ferret (an investigative journalism outfit) has reported that animal rights groups, including Peta, have urged Edinburgh University to stop using the ‘behavioural despair test’. Behavioural despair tests, or Porsolt swim tests, which from now on will be called Forced Swim Tests (FST) are a widely used experiment to measure the efficacy of antidepressants. A mouse or rat is dropped into a beaker of water, heated to around 25-30 Celsius, and the researchers measure how long it keeps trying to stay afloat. It is thought that a happier rodent will fight to stay afloat longer than an unhappier one, which will give up earlier. The University has responded, with a spokesperson telling The Ferret: “We use animals in research only where there are no alternatives and their use is justified on scientific, ethical and legal grounds.” The spokesperson also claimed their work is in compliance with the Animal Welfare and Review Body.

More than 350 million people suffer from depression, making it one of the most common disorders in the world. As many as two-thirds of those who commit suicide have depression. In this way, we can see the need to develop cures for depression: antidepressants are one of a multi-pronged approach to deal with the mental health disorder. Behind the FST lies the logic that the induced inescapable stress triggers immobility, which can be offset by antidepressant treatment. However, many researchers and companies (AstraZeneca and King’s College London are among those who do not use the test) now think that this logic is flawed. A paper undertaking a systematic review of data from preclinical studies employing forced swimming tests writes that “one criticism that may apply to FST is the abundance of ‘positive results’ that contrasts with the failure of antidepressant treatments in some clinical trials”. The paper does, however, conclude positively for the FST.

The question – aside from the dubious logic of the experiment – is also the rights of the rodents. Why should rodents have extreme stress induced in them in the name of science? And, even if we accept this, does it even help? The reductionist methodology that grants science its impressive predictive power seems to fly in the face with something as complex, multifaceted, and subjective as human feelings and depression. The FST seems to rely on the premise that depression is induced by physical stress, but this does not mimic the human experience of depression in most cases – this would explain just some of the discrepancies between preclinical and clinical trials. Having said this, a lot of the antidepressants currently on the market do extend the time a rodent is willing to fight. 

It seems that what is needed is a middle ground: a test which allows a more accurate impression of human depression and is less cruel on the rodent involved. One such test is where the rodent is subject to chronic social stress, called the ‘social defeat’ model. A mouse is placed in a cage with a more powerful, nastier mouse who bullies the smaller mouse. Typically, after repeated exposure, the smaller mouse no longer shows interest in pleasurable activities such as sex or drinking sugary water. This, though still cruel, is nowhere near as cruel as the terror of drowning. Still, researchers admit it is a rough imitation of the complicated mental health disorder.

Overall, the FST is wrong, not only because of the rodent’s suffering, but also the dubious logic involved in the experiment itself and its extrapolation to the human experience of depression.

Image via Wikimedia Commons