Placebo acceptability in chronic pain patients: More dependent on application mode and resulting condition than on individual factors.

INTRODUCTION: Placebo effects can be very effective in certain pain conditions, but their use is still highly controversial. Several studies show that patients would accept a placebo treatment under certain circumstances, particularly when they are informed prior to the treatment or when there are no effective treatment alternatives. This study examines the question, which factors influence the degree of acceptability of a hypothetical placebo application.

METHODS: Patients filled in a questionnaire dealing with placebo applications. Moreover general data, diagnosis, duration of pain, pain ratings and anxiety/depression/stress scores, sleep disorders and opioid intake were collected from the patients` charts. 129 patients (44 men / 85 women, mean age 51.5 years, 18.0-80.9 years) entered the study. All patients had chronic pain syndromes and were treated in an universitary academic interdisciplinary pain center. Mean duration of pain was 14.7 years.

RESULTS: The study did not show significant differences in placebo acceptability among patients with different pain diagnoses or accompanying psychological diagnoses or disorders. Hidden placebo application was considered much more unacceptable for the patients than the enhanced placebo or the open placebo application. An improved condition was associated with less feeling of deception, more trust and less negative mood than an unchanged or worsened condition.

CONCLUSION: Acceptance of placebo as pain therapy is much more dependent on the way of application (hidden or open) or on the resulting condition (improved, unchanged or worsened) than on factors inherent in the individual patients.