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Expectations and placebo responses to caffeine-associated stimuli
Magne Arve Flaten1, Ole Aasli, Terry D Blumenthal
1Department of Psychology, SV-Fak, University of Tromsø, 9037 Tromsø, Norway. magnef@psyk.uit.no
Psychopharmacology
|May 22, 2003
Summary
Expectations of coffee's effects did not fully create placebo responses. While participants expected increased alertness, only caffeine produced significant subjective arousal, with limited support for expectancy theory in placebo effects.
Area of Science:
- Psychopharmacology
- Neuroscience
- Human Physiology
Background:
- The expectancy theory posits that psychological expectations influence physiological and subjective responses to treatments.
- Understanding the role of expectations in placebo responses is crucial for developing effective therapeutic strategies.
Purpose of the Study:
- To investigate whether expectations of coffee's effects control placebo responses.
- To examine the relationship between expected and actual physiological and subjective arousal after consuming coffee or decaffeinated coffee.
Main Methods:
- Twenty participants reported expected arousal increases from coffee.
- Administered decaffeinated coffee or caffeine (200/400 mg) and measured acoustic startle eyeblink, skin conductance, blood pressure, heart rate, and subjective arousal.
Main Results:
- Caffeine significantly increased physiological responses and subjective arousal.
- Decaffeinated coffee enhanced physiological responses but not subjective arousal, despite expectation.
- A positive correlation was found between expected and recorded alertness after decaffeinated coffee.
Conclusions:
- Expectations of coffee's effects did not fully elicit placebo responses for subjective arousal.
- Expectations were dose-dependent, but the placebo response was not.
- The study provided limited support for the expectancy theory of placebo effects.