I have a love/hate relationship with the placebo effect. On the one hand, I simply want my patients to feel better and don’t really care how that occurs. However, since a large part of the placebo effect in veterinary medicine is related to the primary caretaker’s and veterinarian’s perception of how the animal is doing and not on the patient’s own experience, I worry that the placebo effect leads me to overestimate the success of the treatments I prescribed.
As Margaret Gruen, one of the researchers involved in developing a new study design aimed at teasing out the effects of placebos, put it in a North Carolina State University press release:
In veterinary medicine, we’re one step removed from the patient, and so we run into what we call the ‘caregiver placebo effect,’ which is how we refer to a number of factors that result in unconscious influence on owners’ responses. Merely observing behavior can change it, and any changes in daily routine, like administering medication, will affect the way you relate to that animal and change its behavior.
The study was recently published in the Journal of Veterinary Internal Medicine. Fifty-eight cats with clinical and radiographic evidence of degenerative joint disease (osteoarthritis) were enrolled and divided into two groups. All cats received a placebo during the first two weeks of the study, and their owners were aware of what they were giving. During the next three weeks, one group of cats was switched to a pain reliever while the other group continued with the placebo. Owners were aware that the change had taken place but not which group their cats were in. Finally, all cats again received a placebo for the last three weeks of the study, but the owners did not know that a switch had been made.
The results are fascinating. During the middle part of the study when half the cats were on a placebo and the other half were on a pain reliever, all the owners reported that their cats were doing better. The only time that significant differences were noted in the two groups was during the final phase of the study. The owners of the cats receiving the pain medication were able to detect a worsening of their condition when were switched to the placebo while the owners in the placebo group unsurprisingly reported no change.
Increased awareness of the caregiver placebo effect will hopefully lead to better study designs that take its effects into consideration, which will allow me to prescribe only those medications that are truly beneficial to my patients. Also, we all need to be aware of how powerful the caregiver placebo effect can be, particularly when we read anecdotal reports about how wonderful the latest fad treatment is. The caregiver placebo effect makes it next to impossible for somebody who gives a product that makes beneficial health claims to their pet to accurately evaluate whether or not it works.
You don’t think the shadier manufacturers out there are aware of this, do you?
Dr. Jennifer Coates