What is the Forced Swim Test?
The Forced Swim Test is an animal test that involves forcing small animals such as rats or mice to swim in an inescapable beaker of water until they ‘give up’ and float. Some researchers use the test as a misguided attempt to mimic depression or hopelessness in humans.
Why is the Forced Swim Test invalid?
The Forced Swim Test is fundamentally flawed, and evidence shows that floating is actually a learned and adaptive behaviour, one that saves energy and is beneficial for survival. Individual animals who are quicker to float will save energy and are less likely to sink, meaning that animals who more rapidly pick up on this reality, and spend less time struggling, are merely learning this adaptive behaviour quicker.
The Forced Swim Test doesn’t predict how humans will respond to drugs and has no relevance to human depression. The causes of depression are not adequately understood yet - many different factors could contribute to symptoms of depression in humans. Trying to replicate a complex human condition by dropping mice or rats into inescapable beakers of water is questionable, to say the least!
Scientists themselves are speaking out against the Forced Swim Test due to its lack of merit.
People for the Ethical Treatment of Animals (PETA) scientists have found that, in 30 years from 1989 to 2018, experimenters gave animals 47 different test drug compounds before subjecting them to the Forced Swim Test. 36 of them "showed promise" based on the invalid interpretation of the test. But exactly zero of those are now on the market to treat human depression.
An analysis conducted with data from four major pharmaceutical companies found that the Forced Swim Test was less predictive than chance at determining if a compound would have antidepressant efficacy in humans.
A groundbreaking study published in the leading scientific journal Nature highlights the need to end the use of mice in cruel depression experiments. In this study, 64 researchers analyzed the brains of mice and humans and found substantial species differences in types of brain cells and the ways they produce proteins critical to neuropsychiatric function. The authors noted numerous “failures in the use of [the] mouse for preclinical studies” because of “so many [species] differences in the cellular patterning of genes.” Find out more here.
Read more about the invalidity of this test here.
Why do New Zealand universities still use the Forced Swim Test?
In the 1950s, it was thought that the longer an animal in water struggled before ‘giving up’ and floating, the less depressed that animal was. This supposedly showed that the antidepressant had worked and contributed to making the Forced Swim Test become a routine part of testing experimental treatments.
But we’ve learned a lot in the past 60 years – including that the Forced Swim Test is not a valid way to measure if an antidepressant works. In fact, the evidence now shows that the behaviour of the animal in the Forced Swim Test represents a survival strategy rather than a state of ‘depression’.
Find out which NZ universities are using this test here.
Pointless suffering for animals that also harms people
The Forced Swim Test doesn’t predict if new treatments will be effective in humans. This means that antidepressant treatments that might help humans could be abandoned based on the results of this outdated test. More than 95% of drugs that work in animal experiments fail to lead to drugs or therapies for humans and some of the drugs we rely on today would not exist if they’d been first tested on animals.
The Forced Swim Test highlights just how ridiculous the claim is that animal models can predict the human response and go on to save human lives. In the same way mice in cylinders of water with no way of escape, don't accurately model human depression, animals used in cancer, stroke, diabetes research and as a model for any other human illness, is a complete waste of time and resources.
What tests should be used instead?
There are already many reliable methods to test drugs meant for humans without using animals. These include computer modelling of human systems and drug repurposing programmes. According to the Citizens for Alternatives to Animal Research and Experimentation (CAARE) other reliable methods include functional magnetic resonance imaging (fMRI) which has been used to predict which patients will respond best to antidepressant treatment, diffusion tensor imaging and examining brain tissue from deceased donors to identify genes involved in depression and other psychiatric illnesses.
In addition to these humane and scientifically valid methods, more time and resources should be spent on developing additional effective tests. Read more here.
Industry rejects the Forced Swim Test
In December 2018, after talks with PETA, pharmaceutical giant AbbVie committed to not funding or conducting Forced Swim Tests. Pharmaceutical companies Johnson & Johnson (March 2019), DSM Nutritional Products (May 2019), NutriFusion LLC, Astraea Therapeutics and Roche Pharma (July 2019), AstraZeneca and Novo Nordisk A/S (August 2019) Sage Therapeutics (October 2019) and Pfizer (November 2019) have also committed to not use or fund this test in the future.
Johnson & Johnson is the world’s largest pharmaceutical company, Roche is the second largest and Pfizer is the third largest pharmaceutical company in the world. This means that the three top pharmaceutical companies worldwide (in terms of revenue), and seven of the top 20, have committed to no longer use the Forced Swim Test.
This shows that even the pharmaceutical industry is recognising this test as outdated and irrelevant. Now let's make sure NZ keep up with this global shift!
NZAVS and SAFE have joined forces to ask the NZ Government to not only ban the Forced Swim Test in NZ but also to conduct a full review and evaluation on the validity of animal tests used for psychological tests in NZ. To help the many people suffering from addiction and depression, researchers should be looking at human-relevant studies, not torturing and nearly drowning mice and rats.
Noteworthy articles recently published:
Depression researchers rethink popular mouse swim tests in Nature (International Journal of Science)
Letter to the editor: Use of the forced swim test to assess “despair” in Brain Stimulation (Basic, Translational, and Clinical Research in Neuromodulation)
Forced-Swim Test Criticized as Uninformative, Cruel in The Scientist (magazine for life science professionals)