"In practice, for example, one treatment may turn out to be much more effective than another because many more patients actually take it than the other treatment," Olfson said.
Slutsky agreed that comparative effectiveness studies are important. That kind of research, she said, "will help illuminate important distinctions among treatments and help decision-makers make informed decisions regarding treatments for particular conditions."
Kaptchuk said the findings underscore a need to better understand the placebo effect, including how it may be changing drugs' apparent performance in clinical trials. And on a broader level, he said, the results show how complicated scientific research is.
"People tend to think that, you do a scientific experiment and you get certainty," Kaptchuk said. "But it's a lot more complex than that."
Learn more about clinical trials from the U.S. National Institutes of Health.
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