Sometimes when a patient is given a treatment, like an antidepressant, the symptoms go away for awhile, and then come back. This is called a relapse. One reason for a relapse would be that the drug stops working. Another possibility, raised by this study, is that the drug was really working by means of a placebo effect. The placebo effect is something we have all heard of, but we tend to dismiss it as a problem in experiments, rather than an issue in the real world of treatments. The placebo effect is important in both settings.
In an experiment, the placebo effect is well-known potential problem, and good experiments are designed to avoid it. Here is how it works: If you give someone a new drug, or a new kind of therapy, or really any treatment at all, they usually expect it will work. After all, the person giving the treatment, be it doctor, therapist or scientist, is presumed to be some kind of expert. That expectation, that the treatment will do some good, can be a powerful force all on its own. In a depressed patient, the hopefulness that accompanies the expectation of a treatment working may be enough to improve a patient’s mood. That in turn will improve their interactions with other people. Better interactions will also help to improve their mood. So the expectation of getting better really does make the patient better. You can see why this is sometimes called one kind of expectancy effect.
The problem in an experiment is that we want to isolate one variable, the treatment effect, from any other variables, including expectancy effects. It is actually pretty simple to do. In an experiment looking at the effectiveness of an anti-depressant we need to have two groups getting pills, and one group not getting pills. One of the pill groups gets the antidepressant. The other one gets sugar pills, which are the placebos. The third group gets nothing. It is important that these three groups are otherwise as similar as possible. It is also important that those patients getting pills not know whether they are getting the real antidepressant or a placebo. We want the expectations to be the same for both groups.
Now let us imagine that the 66% of treatment group, the one that got the antidepressants. gets a lot better. That sounds good, but it is not really a measure of the effectiveness of the drug. It is really a measure of the drug effects, plus that expectancy effect. If 66% of the placebo group also got a lot better, then it looks like the drug was not effective after all, except by creating an expectation of improvement. If only 10% of the placebo group got a lot better, then it looks like the drug had a lot of benefit beyond just creating the expectation of improvement. We can use a similar logic to estimate the extent of the placebo effect, itself, by comparing the placebo group to the no-treatment group.
Now let’s switch from the world of experiments to the world of treatments. If someone who is depressed seeks treatment from a doctor, and that doctor prescribes some kind of pills, they had better not be sugar pills! The patient has a right to expect the doctor will prescribe something that has proven to be more effective than a placebo. But what does that mean about expectations? Most patients probably expect that whatever the doctor gives them will help them get better, and just like in an experiment, that expectation can be a powerful force in and of itself.
On the face of it, that should be a good thing. The patient’s expectations should combine with the drugs effects to give them a double-whammy. On the other hand, no drug, especially not an antidepressant, is going to work for everybody. And that expectation, or placebo effect, is probably not going to last forever. So what may happen is that some patients, who seemed to be doing well on whatever drug was prescribed, have a relapse some months down the line.
Here’s the question I have, and I really don’t know which answer I prefer. Should a doctor, in prescribing a new antidepressant, be as positive as possible about the potential benefit? In other words, should they try to maximize the placebo effect? Or should they strike a cautious tone, emphasizing that not every drug works for every patient?
Zimmerman, M and Thongy, T. (2007). How Often Do SSRIs and Other New-Generation Antidepressants Lose Their Effect During Continuation Treatment? Evidence Suggesting the Rate of True Tachyphylaxis During Continuation Treatment Is Low. Journal of Clinical Psychiatry (68) 8, 1271-1276.