Factors modifying drug and placebo responses in randomized trials for bipolar mania. Academic Article uri icon

start page

  • 863

end page

  • 875


  • Randomized placebo-controlled trials (RCTs) are standard for assessing efficacy and safety of treatments. We pursued preliminary indications that some factors are associated differentially with responses to placebo or drugs in RCTs for bipolar mania. We meta-analysed data from RCTs to assess influences of study-site count, subjects' age, sex distribution, diagnostic subgroups, clinical features, trial-completion rates, and publication year on mean difference (MD) in mania ratings between intake and final assessments. In 38 RCTs involving 3812 placebo-treated and 6988 drug-treated patients, symptomatic improvement was similar in placebo arms of trials of effective (6.77, 95% CI 5.77-7.76) and ineffective (7.61, 95% CI 5.47-8.75) drugs. Lesser placebo responses (MD) and greater drug-placebo differences (Hedges' g) were associated with fewer study sites, younger patients' age, and male sex. More patients with initial psychotic features and more trial completion in drug arms were associated with greater drug-associated improvement (MD) and drug-placebo contrast (Hedges' g), whereas more mixed-state diagnoses decreased both measures. Identifying modifying factors can support more efficient and cost-effective designs of therapeutic trials. In trials for mania, fewer sites may limit placebo response and enhance drug-placebo contrasts.

date/time value

  • August 2011

Digital Object Identifier (DOI)

  • 10.1017/S1461145710001641

PubMed Identifier

  • 21299919


  • 14


  • 7


  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Antimanic Agents
  • Bipolar Disorder
  • Humans
  • Male
  • Middle Aged
  • Placebo Effect
  • Publication Bias
  • Randomized Controlled Trials as Topic
  • Severity of Illness Index
  • Sex Characteristics