Are Spay/Neutered Pets Depressed

There are have been several viral pieces on the Internet over the past few weeks about whether or not spay/neutered pets may be depressed.

In short – the answer is a resounding “NO!” I think.

Studies do demonstrate that when women’s ovaries are removed for medical reasons, there’s an increased risk of anxiety and depression. Similarly men with amputated testicles (for cancer treatment) may run the risk of mood disorders.

Unlike people, pets don’t pine, “I’ll never be able to have a baby” or “What will my spouse think of me.” For guys, it’s all about us – I suppose – looking south and seeing nothing – sure that’s depressing. I’m not sure dogs inspect themselves in quite the same way Also, dogs and cats are commonly spay/neutered as pediatrics. So, as adults, they’re not likely to have any memory of any surgery. Also, in these instances, the people suffering from depression might be depressed as a result of illness, and/or medical procedures.

Now, listen – I am not completely ruling this idea out. As one article on the web, by Madeleine Johnson points out, Sex hormones are known to interact with the brain in complex ways, and estrogen and androgen receptors in the hippocampus and amygdala seem to regulate mood. Since spaying and neutering can change a pet’s behavior—that’s a big part of why we do it—it’s fair to wonder whether the surgery might also affect an animal’s mental or emotional state. Neutered people are prone to depression. Why wouldn’t a spayed cat feel the same?

It’s true, the Mayo Clinic studied more than 600 women in Minnesotan who had both ovaries surgically removed before menopause, and found they had an increased risk of being diagnosed with depression or anxiety in later life.

According to a 2005 report from the American Psychological Association, rats with sex hormones removed may become depressed. Johnson’s story notes similar research confirming mice become depressed when their sex hormones are removed.

Arguably more compelling – the impact of de-sexing on monkeys. Researchers removed the ovaries of some Japanese Macaques at a National Primate Research Center in Beaverton, OR., where hundreds of females live in close contact with their mothers, grandmothers, sisters, and female cousins. Researchers reasoned these snow monkeys could model mood changes due to ovariectomy without confounding variables like the social stigma of barrenness that might affect women. The center picked 10 females of equivalent rank in the dominance hierarchies and removed the ovaries and uterus from five of them. The other five had their “tubes tied,” so were sterile but still had intact ovaries. Since the monkeys wouldn’t understand the biological ramifications of surgery, and would have similar social lives, any difference between the two groups could be attributed to ovarian hormones.

Here’s what happened: The authors noted that spayed monkeys ate and drank more, and groomed and had sex less—suggesting social impairment and stress. When researchers confronted the monkeys with a black rubber snake, four out of five ovariectomized monkeys backed away and closed their eyes. (The others touched the snake and played with it.) The scientists deemed this peculiar behavior a “non-adaptive” response to threat and novelty, and concluded that the presence of ovarian hormones keeps female macaques calm and socially engaged. Other research (from 2011) on the same Oregon snow monkey troop suggests spaying impacts serotonin levels.

Few research on this topic has been conducted with dogs or cats. In 2006, a small study of German shepherds on a Korean Air Force base showed that female dogs without ovaries were more “reactive” to both people and to other dogs than sexually intact ones, meaning they were more likely to bark and growl when a test dog or person was walked past their kennels. Note the dogs in this study were tested at 5 to 10 months, when this sort of behavior is more likely to occur in any dog. Also, a few other studies report an increase in separation anxiety and noise phobias (e.g., fear of thunder or fireworks) in some dogs and shyness in cats after spaying or neutering, particularly if done at an early age.

There’s still much to learn about spay/neuter, particular early spay/neuter. And I would love to see additional non-invasive research. Having said that, right now – most experts agree (as do I) – benefits of spay/neuter outweigh any risks, as I told Bill Leff of WGN Radio on Monday, October 17.