Endogenous cortisol and conditioned placebo effects on pain - A randomized trial

Area of Science:

• Neuroscience
• Psychology
• Endocrinology

Background:

• Placebo effects are influenced by learning and conditioning, which are modulated by glucocorticoids.
• Previous research indicates that associative learning, including placebo learning, can be affected by exogenous and endogenous glucocorticoids.

Purpose of the Study:

• To determine if daily fluctuations in endogenous cortisol levels modulate placebo effects induced by pain conditioning in healthy males and females.

Main Methods:

• 77 healthy participants underwent a two-phased placebo conditioning paradigm for pain analgesia.
• Participants were randomized into two groups: morning (high cortisol) or afternoon (low cortisol) preconditioning.
• Placebo effects were assessed two days later, with pain reduction compared between groups.

Main Results:

• A significant conditioned placebo-induced analgesia was observed, with a small to medium effect size.
• Cortisol levels differed significantly between the morning and afternoon conditioning groups on the conditioning day.
• No significant difference in pain reduction was found between groups, indicating placebo effects were not affected by cortisol levels during conditioning.

Conclusions:

• The study found no evidence that endogenous glucocorticoid levels, specifically cortisol, moderate placebo conditioning for pain analgesia.
• Daily cortisol fluctuations do not appear to influence the effectiveness of learned placebo responses in healthy individuals.