Studies & Research
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Dogs and the Placebo Effect
Is it all in their heads?


Ariel, my Doberman, lies restrained on her back. She is surrounded by strangers, in a room with frightening smells. In an effort to keep cancer at bay, she has been poked, jabbed and invaded for more than a year and has now developed one of chemotherapy’s dreaded side-effects: an inflamed bladder wall, which is hemorrhagic and painful.

The doctor positions the long needle as the ultrasonographer guides its placement via the monitor. Hugging and kissing her, I cannot watch as the needle plunges into her bladder to retrieve its specimen. Yet I know the moment it happens—Ariel’s eyes dilate like deployed air bags, and she turns and tenderly cleans my face until the hurt is withdrawn. This contact is considered by many researchers to be part of the mechanism of the placebo effect at work in dogs.

Placebo is “the beneficial effect that arises from a patient’s expectations from a treatment, rather than from the treatment itself.” Does the placebo effect exist in dogs? Until recently, the presumed answer was a resounding no, because animals were thought to lack the cognitive capacity to understand the intent of medical care or the power of suggestion, or to have hope of recovery.

What a howl! Such nonsense is summarily dispelled by two pages of technical references underpinning a recent veterinary journal article entitled “The placebo effect in animals,” which documents in detail the existence of the placebo effect in dogs, among other species. A subsequent article, “Effects of human contact on animal health and well-being,” follows up with even more scientific references regarding the substantial benefits of this adjunct therapy.

Both of the articles suggest that the placebo effect in veterinary medicine can enhance the efficacy of medical treatment, and findings make a “strong scientific argument for encouraging in-hospital visitation by owners when animals are hospitalized.”

Experimental studies on the mechanisms of the placebo effect in animals have been underway for at least 70 years. Components of this phenomenon, including belief, expectation and trust, are presumed to be present at a neurobiological level, though cellular mechanisms remain unknown.

In humans, the placebo effect is generally ascribed to one or more of the following: classical conditioning, expectation and endogenous opiates (the body’s own naturally produced pain-relief). In animals, interestingly, a fourth mechanism is also theorized: the effect of human contact. Numerous studies have documented positive physiologic and health effects as a result of animals’ visual and tactile contact with a human. The ability of human contact to optimize an animal’s comfort and well-being provides a strong rationale for pet owners being present for many medical procedures.

A recent double-blind veterinary study involved arthritic dogs randomly assigned to either a treatment or a placebo group. Their response to treatment was objectively assessed by force-plate analysis, which precisely measures the use of individual limbs while a dog is in motion. The result? Fifty-six percent of placebo-treated dogs had an objectively measured, significant, positive response.

When a person strokes a dog, substantial decreases in the dog’s heart rate can be noted. Human contact also consistently elicits major positive changes in canine blood pressure and aortic and coronary blood flow. The placebo effect in animals on immunomodulation, cardiovascular disease, drug withdrawal, tumor growth and much more is well documented. The proverbial bottom line is that an animal’s mental and emotional state has a profound influence upon its physical health. And, human contact has a positive impact on the well-being of animals of all age groups, and produces an array of physiologic, emotional and health effects.

Upon discharging Wendy, my beloved, gentle, 11-year-old Doberman to my care, clinicians at the veterinary school advised me to “take her home and love her, she has two to three weeks to live.” I knew this to be correct. Only a few cases have ever survived Wendy’s untreatable and rare cancer for several months, and those who did required intensive, constant medication. After a month of blood transfusions, a last-ditch effort that in recorded practice has never worked, Wendy became incompatible with all available blood from canine blood banks.



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Submitted by Whisper | February 12 2013 |

Thin ice.

I think it's a stretch to argue for a "placebo" effect in pets, and certainly not in the general animal population that has been used in animal studies. Placebo, as understood on a common-sense level, is the effect of "believing" that some ritual, whether it be taking a pill, or any act or series of actions, indeed, has the power to effect a positive change in bodily function, or dysfunction. There are enough studies in humans to show such a link in humans. The placebo effect, aside from the "fear" of it affecting scientific data, long predated any studies to confirm it, formally. It has been a common criticism of any treatment outside the mainstream of modern medical treatments and has also been used by doctors with some patients; especially those patients considered to have conditions that existed only in their minds.

I seriously doubt that rats and mice, commonly used in medical testing, were stroked and comforted as a pet would be. Even the idea, as argued here, would need to be avoided for the very reasons implied here. One such study for the, still, controversial treatment, acupuncture, (http://www.sciencedaily.com/releases/2011/12/111219150915.htm) doesn't conjure up visions of technicians petting and comforting the rats during the testing. One might contact the authors and find out if any such comfort was given to the rats in the study.

Submitting the idea of a "placebo-like" effect, is just an extension of what "seems" logical. (The stroking could be a whole other study in fact -- mechanical vs. human or another animal, even.) I would argue, that, at best, the stroking is a transference of the emotion of love, not a transference of the owner's belief in the treatment. Even a creation of some kind of "faith" on the animals part would still not be connected to any "belief" by the animal in the efficacy of the treatment.

Considering the vast number of studies with animals, offering comfort as part of the interaction with the animals, during monitoring physiological parameters, is extremely doubtful. If so, the authors should mention it as part of the methodology.

Most medical practitioners, whether physicians for humans OR animals, still, feel a need to show that everything must be explainable by "science" or scientific thinking -- or that, that is their guide. Actually, there are holes in that adherence, such as, the study of vitamin C -- or lack thereof. (See http://orthomolecular.org/library/jom/1991/pdf/1991-v06n02-p099.pdf)

Physical contact affecting an animal isn't the same as placebo in the classical sense. I don't doubt the effect at all. But it isn't placebo.

The whole issue of placebo effect in animals could be cleared up by finding a competent animal psychic. ;)

Submitted by Anand Ghurye | December 27 2013 |

Dear Kathy ,

Thanks for sharing your experience. The placebo effect in human beings has been well documented . Why do we feel that it cannot hold for aninals or for that matter human babies ? The primary reason is said to be our belief that animals lack the cognitive ability to realise the intent of treatment . I believe that on the contrary the animals do it even better as the verbal skills are lacking . They are better mind readers as they have direct access and much heightened senses . So a placebo effect will be all the more powerful in their case .

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