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The placebo effect in agoraphobia--II.
1Department of Psychiatry, College of Medicine, Ohio State University, Columbus 43210.
The Journal of Nervous and Mental Disease
|July 1, 1988
Summary
Agoraphobia patients showed a weak initial placebo response, but this improved significantly over 10 weeks. Most symptom relief occurred early, with phobic measures improving gradually over time.
Area of Science:
- Psychiatry
- Clinical Psychology
- Pharmacology
Background:
- Agoraphobia is a debilitating anxiety disorder characterized by fear and avoidance of situations where escape may be difficult.
- The placebo effect in psychiatric research, particularly for anxiety disorders, is often debated due to potential confounding factors like expectancy and exposure.
- Previous studies indicated a limited placebo response in agoraphobic patients, necessitating further investigation into its temporal dynamics.
Purpose of the Study:
- To evaluate the short-term and long-term placebo response in agoraphobic patients without exposure instructions.
- To determine the magnitude and temporal pattern of placebo effects on panic, anxiety, depression, and phobic symptoms.
- To explore the clinical significance of placebo response over an extended treatment period.
Main Methods:
- A single-blind, placebo-controlled study involving 44 patients diagnosed with agoraphobia.
- Patients received placebo for an initial two-week period, with subsequent analysis of a subsample (n=10) over 10 weeks.
- Symptom severity was assessed using standardized measures for panic, anxiety, depression, and phobic avoidance.
Main Results:
- Initial two-week placebo administration yielded statistically significant but not clinically meaningful reductions in panic and phobic symptoms.
- Over 10 weeks, the placebo response was maintained and increased, with 20-30% of patients classified as marked responders.
- Improvements in panic, anxiety, and depression were predominantly early, while phobic symptom improvement was gradual and significant over time.
Conclusions:
- A sustained and clinically relevant placebo effect can emerge in agoraphobia treatment over a 10-week period, even without specific exposure protocols.
- The differential time course of symptom improvement suggests distinct mechanisms underlying placebo response for different symptom clusters in agoraphobia.
- Findings highlight the importance of considering long-term placebo effects and symptom-specific trajectories in designing and interpreting clinical trials for anxiety disorders.