Placebo Effect in Randomized Trials of Major Depressive Disorder With Psychotic Features: A Systematic Review and...

Area of Science:

• Psychiatry
• Clinical Psychology
• Pharmacology

Background:

• Historically, placebo response rates for major depressive disorder with psychotic features (MDD-Psy) were reported near 0% in the 1980s.
• Recent systematic reassessment of these rates was lacking.
• This study addresses the need to evaluate placebo response trends in MDD-Psy randomized controlled trials (RCTs).

Purpose of the Study:

• To systematically review and reassess placebo response rates in randomized controlled trials (RCTs) for major depressive disorder with psychotic features (MDD-Psy).
• To compare placebo response rates from different eras (1980s vs. 2000s).

Main Methods:

• Systematic review of MEDLINE-indexed randomized controlled trials (RCTs) for MDD-Psy.
• Included studies with placebo or sham control groups.
• Extracted and aggregated response and dropout rates for placebo versus active interventions.

Main Results:

• Pharmacotherapy RCTs from the 1980s showed 0% placebo response (0/12) versus 34.2% active response (13/38).
• RCTs from the 2000s demonstrated a significant increase in placebo response to 33.6% (114/339), with active response at 39.9% (149/373).
• Dropout rates were comparable between placebo (30.1%) and active interventions (29.8%) in recent trials.

Conclusions:

• Placebo response rates in MDD-Psy RCTs have markedly increased from the 1980s to the 2000s.
• Potential methodological issues in recent RCT designs may contribute to higher placebo response rates.
• Current interpretations of MDD-Psy trial results must account for substantial placebo effects, especially in trials lacking pure placebo conditions.