Placebo Effects on Stress, but Not on Pain Reports. A Multi-Experiment Study

Area of Science:

• Psychology
• Neuroscience
• Pain Research

Background:

• Contextual factors like participant and experimenter sex can influence placebo effects.
• This study investigated how participant and experimenter sex modulate placebo effects on experimentally induced pain and stress.

Purpose of the Study:

• To determine if participant sex influences placebo analgesia and stress responses.
• To assess if experimenter sex impacts placebo effects on pain, stress, and blood pressure.
• To examine these influences using within-subjects and mixed designs across two experiments.

Main Methods:

• Two experiments were conducted involving painful stimulations and placebo cream application.
• Experiment One used a within-subjects design with placebo and natural history conditions.
• Experiment Two employed a mixed design with placebo, cream-control, and pain-control groups, involving male and female experimenters.

Main Results:

• No significant placebo effect was observed for pain perception.
• Placebo effects on stress were moderated by participant and experimenter sex.
• Female experimenters reported lower physiological and subjective stress, and higher effectiveness expectations compared to male experimenters.

Conclusions:

• A distinction exists between placebo effects on pain versus associated stress.
• Experimenter sex significantly impacts stress outcomes and expectations in placebo studies.
• Findings suggest female experimenters may enhance placebo effects on stress and perceived effectiveness.