Does neutering make your pet depressed?

For ages, pet owners have been neutering their pets for fear of unwanted offsprings. As is evident, neutered females are relatively unlikely to have breast cancer and males have lower risks for getting a list of diseases. But does neutering cause mental issues in pets? The question is not hard to understand: sex hormones such as estrogen and androgen control mood. So if a pet is spayed, does it also cause depression or mood disorders?

The way scientists have been testing anxiety and depression in animals, for example rodents, is by forcing them to swim. In this test called “forced swim”, what is measured is how long it takes a mouse to stop trying to escape from a bucket of water. The less time it takes for the mouse to stop trying the more depressed the mouse is. Studies have shown that mice without ovaries couldn’t pass the forced swim test, and the same goes for male rats. Interestingly, in the brains of rodents whose gonads are removed, they tend to show reduced neuronal growth in their hippocampal area.

Recently studies have been done in primates. Researchers removed the ovaries of some Japanese macaques who lived with their mothers and other female relatives. They removed the ovaries from five out of ten females of equivalent rank and the other 5 were tubes tied—meaning that they were sterile but their ovaries were still in place. The difference between the group would demonstrate the effect ovarian hormones have.

It turned out that spayed monkeys ate more and had less sex—a sign of social stress and stigma. When the monkeys were presented with a fake rubber snake, 80% of the monkeys who had their ovaries removed backed away while the others took the snake and started playing with it as a toy. This shows that ovariectomized monkeys dealt with novel stimuli in an odd way and may be impaired in that sense. It was concluded that ovarian hormones made female macaques more calm and socially active. Being neutered also significantly impacts their serotonin levels.

So what about cats and dogs? A study was done with German shepherds where the ones that had ovaries removed were more easily agitated and barked more when another dog walked past them. They also showed separation anxiety and fear towards unknown noise.

To neuter or not to neuter? Maybe it’s time for us to start prescribing antidepressants for pets.

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