Pets and the Placebo Effect: Part 1

By Jennifer Coates, DVM on Nov. 26, 2012

I often wonder what percentage of my veterinary successes are a result of the placebo effect.

I’m sure you’ve heard of this sometimes irksome aspect of medicine and medical research, but just so we’re all on the same page, let me pass along the way in which the journal Scientific American explained it:

In recent decades reports have confirmed the efficacy of various sham treatments in nearly all areas of medicine. Placebos have helped alleviate pain, depression, anxiety, Parkinson’s disease, inflammatory disorders and even cancer.

Placebo effects can arise not only from a conscious belief in a drug but also from subconscious associations between recovery and the experience of being treated — from the pinch of a shot to a doctor’s white coat. Such subliminal conditioning can control bodily processes of which we are unaware, such as immune responses and the release of hormones.

Researchers have decoded some of the biology of placebo responses, demonstrating that they stem from active processes in the brain.

In veterinary medicine, I suspect the placebo effect works in several different ways. First of all, some of my patients seem to understand that all of the crazy things their owners and I do are aimed at helping them. If an animal thinks something along the lines of, "Oh good, these people finally understand that I don’t feel well and are trying to help," I could see how the same neurologic, endocrine, and immunological changes that are at work in people could play a part in a pet’s healing.

This might be especially true if an animal had positive experiences with medical treatment in the past. Say, for instance, a dog previously had an acute injury and received an oral NSAID (nonsteroidal anti-inflammatory) that relieved his pain. I wouldn’t be surprised if the dog were to be injured again and we gave him a tablet that contained only inactive ingredients but looked, smelled, and tasted the same as his previous medication that he might experience some pain relief from the placebo effect.

Another form of the placebo effect also comes into play when treating companion animals. Many times, the way in which veterinarians measure the effect of treatment is to ask owners if they think their pets’ condition is improving and/or by making subjective judgment calls ourselves. Here’s an example. I diagnose a dog with osteoarthritis and start him on an NSAID and a chondroprotective joint supplement. A week or two later I either call the owner to see how the dog is doing or see him for a progress check. In either case, the consensus is that his condition has improved. All the people involved in the patient’s care are happy with the results, but how much of the supposed improvement is actually caused by our assumption that the dog would get better with treatment.

A recent study looked into the question of how prevalent this "caregiver" placebo effect is in both owners and veterinarians during the evaluation of dogs for lameness. More on this tomorrow.