#FactCheckNeeded: What irresponsible journalism fails to mention about the Forced Swim Test

January 23rd 2020

It’s tempting to say that we live in an age of misinformation, but hasn’t it always been thus? For many years false claims were expressed in books and magazines or orally, in situations where no-one could whip out a phone and fact check what they were hearing. Most of this has just jumped off the paper and moved online where it can amplify in a forum, subreddit or similar virtual echo chamber. However, it is also now easier to check those claims.

Now, like then, the public has to pick through the noise and count on credible sources if it wants to know what’s going on, and one of the most respected has always been the specialist correspondents working for news titles. These, we all hope, take the time to really get around every issue, and we count on them to be wily enough to spot weasel-words used by campaigners to mislead.

That, unfortunately, is not always what we get.

A good example has been the recent coverage on the Forced Swim Test (FST), where rodents are forced to stay afloat in a tank of water for several minutes until they become immobile. The assay is the focus of a sustained campaign by PETA, which has found it a good campaigning tool because its harms are easily exaggerated. The test has also been misused by scientists in the past and there are serious questions about its scientific validity when used for certain applications.

Source. Behaviors studied in the forced swim test. Click to enlarge.

This does not mean that the FST is useless, however. Campaign groups like to paint experimental methods as either a panacea or worthless, when we should be thinking about methods as different tools. A hammer on its own will not help you tighten a bolt, and a spanner isn’t intended to help you drive a nail, but that doesn’t make either a bad tool when properly used.

Thus we, the public, can understand that when scientists criticize a method, it is firstly in the context of how it is used. Secondly, we can ask whether the study was well-designed, and we can be critical if it was not. There are a number of things to get right before using the forced swim test. Are you using mice or rats? What is the purpose for using the test and what strain of mouse or rat are you using? Some selections of these few options may be inappropriate and thus change your results.

So, assuming the Forced Swim Test (FST) is appropriate and well-executed, what are the key points the public should know about it?

  • Firstly, the animals are continuously monitored and not allowed to drown. The test is typically halted after six minutes for mice and after up to 15 minutes for rats—or earlier if the animal begins sinking. The length of time originally suggested by the inventor of the test was a maximum of 5 minutes for rats and 6 minutes for mice.
  • Secondly, it is used in a variety of ways including drug testing, testing the effect of genetic manipulation and behavioral preconditioning.
  • Thirdly, it is discouraged by regulators for many avenues of research. The US National Institute of Mental Health (NIMH) has stated that “these tests in particular are recognized by many scientists as lacking sufficient mechanistic specificity to be of general use in clarifying the neurobiological mechanisms underlying human depression.” The NIMH still funds studies that use the FST, however, because when properly used it can be ‘crucial’ to answering other scientific questions.
  • Fourth, it has been useful in suggesting the efficacy of selective serotonin reuptake inhibitors (SSRIs)—a class of antidepressants that includes Prozac. It has provided critical pieces of the puzzle in its other applications, too.
  • Fifth, it is not the only assay used in most studies. The results from FSTs are considered alongside those from various other methods and can suggest a direction or corroborate other findings from the lab bench, epidemiology study or other scientific papers. Again, it provides a piece of the puzzle rather than itself being the whole picture.
  • Sixth, it is licensed as a ’severe’ experiment if exhaustion is the outcome (see page 21). In many countries, like the US and UK, experiments are balanced against the likely suffering and information likely to be produced.
  • Lastly, it’s widely accepted that it’s been misused as a technique (by neglecting the importance of water temperature, or using it as the only tool to test for depression rather than using a diverse set of tests) in the past, with the substantive criticisms being led by the scientific community itself. Particularly in the US in the noughties (2000s), adding behavioral data to your study was a good way of getting research published in journals.This misapplication partly explains its alleged ‘failure rate’, when it is not the test per se but how it was being used that was at fault.

What all this means is that the FST is being used less and less as inappropriate uses are weeded out. Many of the campaign ‘wins’ for PETA in terms of companies and institutions ‘ruling out’ use of the FST are a stylised way of saying that those companies and institutions weren’t intending to use that method anyway.

It’s like asking girl scouts if they intend to test their cookies on a beagle. When the answer comes back ‘no’, you may feel that you have saved a ‘dog’ but the fact is you did nothing.

So it was with King’s College London, which responded to a Freedom of Information (FOI) request from PETA asking how many mice it used in FSTs. KCL responded “We have not performed the forced swim test on mice since 2015 or have any intention to do so in the future as we believe there are better behavioral tests available, which are less stressful for the mice.”

This doesn’t mean the FST will not be used if it is important and appropriate, although it will not be used on mice for that purpose.

British broadsheet The Daily Telegraph was the only semi-respectable paper to run the story, but sadly took the KCL quote as their being the “…first university in the world to formally end ‘cruel’ mouse swimming test.” The FST was, it said, ‘widely discredited’. The FST methodology was described as “small animals are placed in inescapable beakers filled with water and made to swim to keep from drowning”. The FST’s mixed results with regard to modelling the effects of drugs on depression made it a ‘poor predictor’, apparently. The other ways the FST is used were not alluded to. The FOI request transformed into “…discussions with the animal charity Peta”*.

The sentence “Yet, the test has been heavily criticized by scientists who argue that floating is not a sign of depression or despair, as some claim, but rather a positive indicator of learning, saving energy, and adapting to a new environment” might make one wonder who these scientists are, but we’re not going to find out because the unsubstantiated quote is from this PETA press release.

We’re all busy people with limited time to get our heads around topics that we’re not directly involved with, and this kind of spin, in a broadsheet of all places, doesn’t get the public any closer to understanding what’s going on.

Although a good rule of thumb for the public is not to take anything anti-research groups say at face value, when in doubt people can also tag articles with #FactCheckNeeded. Meanwhile,  a good rule of thumb for a credible science correspondent for any newspaper has always been, ‘if you don’t understand, ask someone who does’. You can also earn a status as an authority by doing your own research into a topic as we have done here and getting all of the relevant facts. The result may not be as sensational but it is more likely to be true.

~Speaking of Research

*Just to round off the calling out of misinformation spree, PETA isn’t strictly a charity, but a company/charity hybrid. In the UK, antivivisectionist organisations are not allowed to be charities since their aims are not charitable and their ethics exist in a closed-loop worldview where they’re ‘right because they’re right’.