The forced swim test (FST) is also known as the behavioral despair test. It is common in the study of depression and antidepressant drugs. The test is used to assess depressive-like behavior in rodents, such as mice and rats, by measuring their response to a stressful and inescapable situation.
How it works:
A rodent, usually a mouse or a rat, is placed in a clear cylindrical container filled with water. The water is deep enough that the rodent can't touch the bottom with its paws, and the rodent can't escape or rest.
The rodent is left in the water for a fixed period (usually about 5-10 minutes), and its behaviors are observed.
Researchers monitor and record the following behaviors:
Active Swimming: The rodent makes active movements to try to escape or reach the sides of the container.
Passive Floating: The rodent stops swimming and adopts a floating posture, making only minimal movements to keep its head above the water.
Immobility: The rodent becomes immobile, floating in a stationary position without making any further escape attempts.
The data measurement in the FST is the duration of immobility. Longer periods of immobility indicate depressive-like behavior, while more active swimming and less immobility are indicate more resilient and less-depressive behavior.
The forced swim test is based on the hypothesis that when rodents are exposed to an inescapable and stressful situation, they try to escape, but when they realize there is no escape, they become immobile (called "behavioral despair"). This test is used to screen antidepressants, since they typically reduce the duration of immobility.
It's difficult to say if this test is a valid model for human depression, but there are definitely relevant takeaways from it. The inescapable and stressful situations that humans experience as well as their moods are far more complex than those in a rodent. It also may not take into account the survival instinct of humans to keep swimming to stay alive.