According to a study published in the June issue of the journal Health Affairs, there has been a decline in the extent to which new medical treatments are shown to be significantly more effective than placebos. The findings, says study co-author Mark Olfson, MD, MPH, “suggest that medical breakthroughs that offer large benefits above placebo are becoming less common. As a result, now may be a good time to emphasize research that compares established treatments with one another.”
The study authors randomly selected and analyzed 315 placebo-controlled trials that were reported in four leading medical journals between 1966 and 2010. They found that the average effect size, as measured by the odds ratio (which compares the odds of an outcome resulting from the treatment with the odds of that outcome in absence of the treatment) decreased from a peak of 4.51 (1971–80) to 1.36 (2001–2010).
While placebo-controlled studies are considered to be the gold standard for establishing treatment efficacy, the dwindling effect size over the roughly 40-year period supports the view that renewed attention should be given to research that compares treatments already known to be effective, in terms of outcomes that matter most to patients.
In light of the current study, notes Dr. Olfson, professor of clinical psychiatry at Columbia Psychiatry and a research psychiatrist at the New York State Psychiatric Institute, comparative effectiveness research may be an important direction for future clinical research. “With apparently declining yield from placebo-controlled studies, it makes good sense to place greater emphasis on comparing two or more treatments that are known to be effective, to evaluate whether there are meaningful differences in their tolerability, safety, and costs.”