Placebo Effects in Alcohol, Cocaine, and Methamphetamine Use Disorder: A Systematic Review and Meta-Analysis.

Area of Science:

• Psychiatry
• Clinical Psychology
• Neuroscience

Background:

• The placebo effect is recognized in psychiatry, but its impact on substance use disorders (SUDs) treatment is not well-defined.
• Understanding placebo responses is crucial for designing effective clinical trials and treatments for SUDs.

Purpose of the Study:

• To evaluate changes in craving scores within placebo groups in randomized controlled trials (RCTs) for adult SUDs.
• To synthesize existing evidence on the placebo effect on craving across different SUDs.

Main Methods:

• Systematic search of eight databases for placebo-controlled, double-blind RCTs assessing craving in SUDs.
• Included studies published in English, Dutch, Spanish, or German, focusing on craving, addiction, and placebo search terms.
• Extracted data and calculated standardized mean differences (SMDs) for pre-post craving scores in placebo groups.

Main Results:

• Nine RCTs involving 495 participants across alcohol, cocaine, and methamphetamine use disorders were analyzed.
• Craving scores significantly decreased in the placebo group for alcohol use disorder (SMD=0.93).
• No statistically significant reduction in craving scores was observed for cocaine (SMD=0.61) or methamphetamine use disorder (SMD=0.44), with wide confidence intervals indicating uncertainty.

Conclusions:

• Placebo treatment demonstrated a trend towards reduced craving across all studied SUDs, with statistical significance only in alcohol use disorder.
• The limited number of studies for cocaine and methamphetamine use disorder necessitates caution in interpreting results.
• Findings suggest the placebo effect's potential role in SUDs treatment and can inform future RCT designs and personalized treatment strategies.