Are active placebos necessary

A corollary of this question is: Is this a way of increasing the proportion of placebo responses? Several recent reviews suggest that an active (that is, symptomatic) placebo is necessary to estimate antidepressant efficacy. (15,46) This position was originally proposed by Thomson, based on a review of double-blind studies of tricyclics using an active and an inactive placebo. (47) Thomson concluded that the medications were found to be effective in 14 per cent (1/7) employing an active placebo but in 59 per cent (40/68) using an inert placebo. The obvious implication is that in the absence of an active placebo (usually atropine) the estimate of antidepressant efficacy is inflated. Another four studies with an active placebo, in addition to the six originally reviewed by Thomson, were found. (4 d9,50,5!,5 5 ^d5.55. and 57) The rationale for giving an active placebo would be to augment the effect observed with an inactive placebo, thus making it more difficult to attribute drug benefit to the non-specific, rather than specific, drug effects. Therefore, if side-effects are relevant in enhancing therapeutic effects, a higher response rate would be anticipated with an active placebo. This is not the case. When the data were pooled from those studies in which a judgement could be made about the proportion of responders, it was found that 22 per cent (61/276) of the patients on active placebos were judged to be responders. ^M9,5,5 ^.M4,5. ,5 and 57> One study,(53> with a placebo response rate of 6/90, appears to be an outlier. Removing this, the remaining studies have a response rate of 30 per cent (55/186). This is virtually identical to the response rate seen with inactive placebos. In general, no method has been identified that enhances the placebo response rate within a patient sample.

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