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does the placebo effect exist in pets?

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Posted by Dr. Kim on Dec 07 2016



What’s a placebo, you ask? A placebo is a treatment that has no physiological benefit. It’s like a “blank” pill, and it’s often used in drug studies to test the potential effects of a medication in humans.

Placebo effect is the phenomenon where people believe they’ve experienced an effect after receiving a placebo. Usually, they don’t know whether they’re getting the placebo or a real drug. Their condition improves simply because they think they’re taking a medication that will make them better.

the power of placebo

I once saw a story about a woman taking a placebo for pain. After taking it, she reported that her pain went away. The placebo affected her so much that even after she found out she was taking a placebo, she continued to take it! That’s how strong her belief was.

The story got me thinking about the placebo effect in pets. Surely it doesn’t exist, because pets aren’t really aware of the benefits a pill may have for them? Imagine my surprise when I found there’s actually some controversy surrounding the placebo effect in animals, and that it may, in fact, exist!

brain benders

You recall Pavlov and his dogs, right? Every time he rang a bell, the dogs were fed. This went on for so long that the dogs became conditioned to salivate every time the bell rang, as if they were expecting food.

This kind of conditioning may explain why the placebo effect happens in some pets. Take these findings for instance: dogs given a morphine injection would vomit, defecate and sleep. After multiple rounds of morphine, researchers switched the injection to saline, and the dogs STILL vomited, defecated and slept. Eventually, the dogs would exhibit these behaviors as soon as the injector walked in the room. That’s the power of conditioning.

In another study, mice with an increased chance for an autoimmune disease were given immunosuppressing injections. After a while, a placebo was given instead. Incredibly, the immune system reacted the same way as when the rats received the actual drug, and as a result, disease development was delayed. This is a real result from an injection of, basically, water.





all in your head?

Just when I started to become a believer, another study filled me with doubt. In this study, dogs with arthritic pain were given a either placebo or carprofen, a popular veterinary NSAID. Owners reported the effects on their dogs’ pain level, and researchers used force plate examination to measure how hard they walked on the ground.

They found that the placebo effect did occur, but not to the dogs — to the owners. Owners whose dogs were given placebos reported that their furry friends were less painful. But almost 45% of the time, researchers found that the dogs were not, in fact, less painful. This is called caregiver placebo effect.

mind scratchers

These studies and findings raise some ethical questions, especially in the field of non-traditional treatments like acupuncture and homeopathy. Is the treatment really working, or is it just the belief that it’s working? And does it even matter, if the end result is a patient who feels better?

But these studies also raise questions for traditional medicine, too. If some pets get better “just because,” should we be sending home any medication at all? Clearly, there are specific needs for medication in many cases, but we also know that some dogs will stop vomiting simply by coming into the exam room. The human mind is a powerful thing, and maybe our four-legged companions have this in common with us.