It may come as a major surprise to you but depression actually does exist in the animal kingdom also. And depression has deep roots in the animal kingdom, so deep that you even find it happening in insects such as the little fruit fly.
Notably when animals, in general, find themselves up against an impossible situation or circumstance, then you tend to find them hunkering down and giving up. They may even develop eating disorders or sleeping problems, or worse such as stomach ulcers. And this behavior has now also been noted in insects. A group of researchers from the Rudolf Virchow Center in Würzburg, Germany have discovered that flies exhibit the same sort of depressed behavior.
And the good news with this discovery is that fruit flies can become the ideal candidate to try testing drugs that are made for treating depression.
The team looked at many situations, one of them was fighting. It was noted that a male fruit fly that lost a fight to another male, would become severely depressed. In fact, it was so evident the fruit fly would become extremely sad because it would stop fighting completely. Even when annoyed by a fly that it could usually easily beat in a fight. This behavior showcases the definition of depression: the feelingness that everything is hopeless and there is no reason to continue.
Another reason for depression was when being rejected by female fruit flies, this could also cause a male fruit fly to give up. It seems that even insects need love and companionship to keep themselves happy.
The team also tried putting them into situations out of the flies control, such as being trapped in a dark box that was heating up severely. They noted that after some panic, the flies would realize they were stuck & start to move extremely slowly as in a depressed state. Hopefully, this discovery by these German doctors and scientists will help the innovation of medicine and drugs produced to cure depression.