Drug response placebo effect

To answer this question, the regulators conducted their own meta-analysis of some of the data in their files. Their results were very similar to ours. They agreed that the average observed difference in improvement between drug and placebo is only about two points on the Hamilton scale, and their data also showed that most of the drug response could be explained as a placebo effect. Nevertheless, they argued that they had shown that the drugs were better than placebos, not only statistically, but clinically as well. 

There is yet another possibility. The general assumption is that the effect of a drug adds to the placebo effect, so that the total improvement that patients experience is the drug effect in addition to the placebo effect. This assumption is implicit in the design of placebo-controlled clinical trials, in which the drug effect is assessed as the difference between the response to the drug and the response to the placebo. Anne Harrington, an historian of science at Harvard University and the London School of Economics, calls it the oil-and-water hypothesis. 

The placebo effect in asthma is one of the most well-studied and robust placebo effects on physiological function. The wheezing that sufferers of asthma experience is accompanied by a constriction of the bronchial airways that makes it difficult for them to breathe. Asthma medications dilate the bronchial tubes, making it easier to breathe, but a large number of studies have shown that placebos can also affect bronchial dilation. In fact, about two-thirds of the response to real asthma medication is also produced by placebo treatment, leaving about one-third of the effect as a true drug effect.40... 

You might find some of this material tough going, and if you are willing to take my word for the significance of these factors, you could just skip over these parts. But I thought it important to document my claims about how placebos work. Just as I have documented my claim that most of the antidepressant drug response is a placebo effect and that the remainder is in all likelihood an enhanced placebo effect, so here, too, I present the details of the research upon which my conclusions about the way placebos work are based. 

The placebo is useful in (a) distinguishing the pharmacod)mamic effects of a drug from the psychological impact of the medication and the environment in which it is given (the "halo" effect of the enthusiastic, or pessimistic, research clinician). It is well known, for example, that the placebo effect in major depression is as high as 30% while that of an effective antidepressant is approximately 60% of the optimal response. This statistic illustrates the importance of placebo-based studies in evaluating the efficacy of a new psychotropic drug. 

It is widely accepted that two placebo-controlled pivotal studies are necessary, although it is not clear whether this is a mandatory regulation in the FDA or EMEA regulations. There is, however, a certain insurance in this approach as studies, even of drugs that are effective, can occasionally fail to show a statistically positive result if the treated population somehow deviates from the norm or if the placebo response is unexpectedly increased. In Europe the use of an active comparator in a pivotal study is more common. 

Thus, Lind showed the importance of the comparative trial and Evans and Hoyle showed the importance of the placebo effect in evaluating drug response. Gold et at. then showed the importance of observer bias and introduced the concept of the double-blind study in 1937 in a study of treatments for angina patients. They wrote ... 

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