High placebo-response rates in trials of bipolar mania treatments piqued the curiosity of researchers, who decided to study the matter through modeling in hopes of minimizing it. Findings suggest a profile of manic patients who are less likely to improve with placebo, or to show greater drug-placebo contrast, says Medscape Today.
Researchers from Dokuz Eylül University in Turkey, as well as Harvard Medical School and the International Consortium for Bipolar Disorder Research in Boston, performed a meta-analysis to identify factors that might limit placebo response in randomized trials of single treatments. The study used unrestricted maximum-likelihood mixed-effects metaregression modeling to assess such influences as study-site count, subject age, sex distribution, diagnostic subgroup, clinical features and trial completion rates. Drug-placebo differences in outcomes were also analyzed, as was the rate of response to the drug and placebo.
Researchers identified 38 randomized controlled trials and 56 placebo comparisons of 17 active drugs. Most trials involved multiple centers.
Characteristics of low-placebo-response trials include fewer study sites and involve younger male subjects having psychotic features. "We propose that this aspect of trial design is readily accomplished and should improve the efficiency of randomized controlled trials, at least for mania," the authors conclude.
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