Results of a new study accepted for publication in the journal Pain suggest that high, and increasing, rates of placebo response may be contributing to the escalating failure rate in clinical trials of drugs intended to control neuropathic pain. An interesting finding of the study is that the increase in placebo responses appears to be confined to trials conducted in the US. The study, conducted by researchers at McGill University, Montreal, examines 84 clinical trials conducted worldwide since 1990. The team found that pain reduction reported by patients in the placebo group increased to an average of 30% reduction in pain levels over the period.
In examining aspects of the clinical trials that might explain the noted changes over time, the study found that in the US—but not outside the US—trials became longer and larger. Other possible factors, according to the authors, could be the existence of direct-to-consumer drug advertising in the US (New Zealand is the only other country in the world that allows this), the greater spread of for-profit “contract research organizations” in the US, and perhaps greater exposure to the placebo concept in popular media in this country. The effect, they note, is to elevate the failure rate of US based trials, as it becomes harder to differentiate response rates between the trial drug and placebo.
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Read a news story about the study findings, with link to the journal article, here.