Veterinary Notes

The power of the placebo effect April 22, 2009

The placebo effect is when a harmless substitute is given instead of genuine therapy and is still successful in curing patients. The placebo effect has been known to doctors for hundreds of years. The first medical reference to a placebo was in 1772 (http://is.gd/tQzn). During the Second World War, there were reports of doctors in military field hospitals successfully treating injured soldiers with simply saline (salt water) injections, once they had run out of strong painkillers like morphine. Surgeries were even performed on casualties using only saline resulting in effective pain relief!

The power of the mind is amazing. There are numerous examples of people reacting to placebos. For example, people have been given non-alcoholic drinks, which they thought were alcoholic and then appear to become drunk later. Also others have had different responses to the same harmless compound, depending on whether they were told that the tablet was a stimulant or sedative.

It has been reported that up to 80% of patients can benefit from placebos for certain conditions like depression and pain. On the other hand, in other diseases like diabetes, it has been shown to have no worthwhile benefit. The placebo is very important for analysing whether a treatment, such as a new drug or surgery, actually has any true benefit. For example, most trials compare a new drug against a placebo (such as a sugar pill) for treating certain conditions and the results are compared. If the drug is no more successful than the placebo, then it is reasonable to assume the drug has no true medical benefit.

There is controversy regarding whether there actually is any beneficial placebo effect. In 2001, some researchers compared many trials, where genuine therapy had been given to patients, in addition to no treatment at all and a placebo treatment (http://is.gd/tQwm). Their results concluded that placebos seemed to be no more effective than no treatment at all. However, their study looked at the placebo for all sorts of diseases e.g. diabetes (which is known to not benefit from a placebo), as opposed to specific conditions such as depression and pain, where the brain plays a vital role. Also, the placebo works by the patient actually believing that the treatment works. Obviously, the more convincing the placebo seems, the more effective the response, e.g. injections seem to work better than pills.

The most important variable in the effectiveness of a placebo seems to be the attitude/belief of the doctor administering it. One study showed amazing results when one group of patients were given a firm diagnosis and told that they would soon be better, whereas the other group received a vague diagnosis and no assurance about recovery. Both groups had some patients receive medicine whilst others received no treatment at all. 64% of patients with a positive consultation got better compared to only 39% of patients with no clear diagnosis/assurance. There was no difference in the recovery rate regardless of whether medicine was given or not! Therefore, doctor’s attitudes seemed more important than the actual medicine.

The placebo effect does not only apply to the human medical field. There are several studies showing that belief in a placebo isn’t always necessary but a response can be conditioned. Rats were given injections of cyclosporine (immunosuppressive drug) to prevent transplanted organs being rejected (http://is.gd/tQlr). At the time of cyclosporine injection, the rats were fed water sweetened with saccharin. The rats were conditioned to associate the cyclosporine with the sweet drink so that later, the rats were given only the sweet drink but no drug and the rats immune system continued to act as if under the influence of cyclosporine. The same results have been obtained with humans allergic to dust using antihistamines and a novel drink (http://is.gd/tQjf)

The placebo has also also been used for surgery. This video is very interesting; patients underwent knee surgery for painful arthritis. Patients that received “sham surgeries” improved as much as those who had the real surgery performed.

The advantage of a placebo effect is that by carefully using the placebo response, we can lower the dose of drugs used without reducing the effectiveness. This obviously has the possible benefit of reducing harmful side effects and the cost of expensive drugs. So how can it be applicable in the veterinary field? One application could possibly include pets on long term medication e.g. painkillers for arthritis or steroids/cyclosporine for allergies. Perhaps, we could give non-steroidal painkillers (NSAIDs) always with a distinctive tasting food e.g. liver and initially full dose every day. After a period of conditioning, the liver continues to be fed daily but maybe the NSAID every other or third day.