Dr David Hamilton Home Page

Expectation vs Conditioning in the Placebo Effect
(www.drdavidhamilton.com)

Recent Studies on the placebo effect have broken it down to two levels: 1) The level that affects the level of pain or the movements of muscles, and 2) Immune, hormone, and respiratory function.

When a person receives a placebo, believing it to be a real drug, they generally expect that symptoms will change. This is called EXPECTATION and is strongest for level 1 changes; that is, for pain relief or changes in muscle movement (e.g. Parkinsons). Relief often comes on a single administration of a placebo. But for level 2 changes (immune, hormone, or respiratory changes), the effect of this type of placebo is less effective. Patients need to be CONDITIONED over time to believe that something will happen.

For instance, in one experiment volunteers were repeatedly given a drink containing an immunosuppressant known as a cyclosporin A, which would weaken their immune systems. And it did. Over time, by having the drink over and over again, the volunteers were conditioned to believe that the drink would suppress their immune systems. So they were then given the same drink but containing no cyclosporin A. Again, their immune systems weakened and this was because they had built up a belief that the drink would have this effect.

And of course, conditioning also gives relief at level 1 too. Some recent research has shown that placebo analgesia is ‘finely tuned’ by previous experience. So in other words, if you expect a medicine to work or not work, it’s effectiveness will be strongly influenced by whether you expect it to work or not.

For instance, in a recent experiment, volunteers received pain stimulation and then a placebo. But they thought the placebo was an analgesic drug that would reduce the pain. So, over time the researchers gradually reduced the intensity of the pain stimulation so that the patients believed that it was the drug that was reducing the pain. This way they were conditioned to believe that the placebo was a powerful drug.

The experiment found that volunteers who had been so conditioned would receive pain relief within minutes after painful stimulation when they took a placebo and the effect would last for 4-7 days.

From my research over the years I have concluded that the placebo effect mostly boils down to a person’s level of belief. Conditioning simply strengthens belief. Level 1 and 2 (these were my assignments, by the way......researchers simply refer to them as surface or less conscious processes....I thought level 1 and 2 were easier to make sense of) symptoms are simply used as a black and white type method of showing the different effect of expectation vs conditioning. But there are always exceptions to the rules. People are different. Some are more suggestible than others. Some generate much stronger or weaker beliefs. Here’s a real-life example of the power of belief:

A friend of mine had bad hay fever. I suggested they get some locally produced honey because by taking a spoonful a day they should become sensitised to the local pollen. Anyway, it worked and after about 5 days the hay fever symptoms were gone completely. But then about 3 weeks later an expert on TV gave a caller some advice that local honey takes about 3 months before it starts working. Guess what happened? My friend’s hay fever returned.

Recognising the psychological effects, I told him that the expert wasn’t involved in science. It’s not their specialty. It was probably just an off the cuff remark. I also suggested that my friend might have even received one of last year’s batch of local honey, since he did buy it right at the start of the summer. The shop might have been using up last year’s stock so it might contain a different spectrum of pollen. He said he would go get some fresh stuff. Guess what? He did and the hay fever disappeared again.