Conditioned Placebo Effects and the Treatment of Hypertension

Project Background and Goals:

The purpose of this study is to investigate the critical question as to whether placebos can have a therapeutic effect in the treatment of hypertension. The study will compare the unconditioned and conditioned effects of placebo capsules in the treatment of patients with borderline hypertension (BH).

This study was designed in response to a request by the National Institutes of Health for research on the placebo effect in clinical practice. It has been suggested that conditioning is an inherent component of most pharmacotherapies and that the “placebo effect” represents a learned response. Placebo therapy is a standard component of antihypertensive drug trials, partly because of the need to identify drug-related side effects, and because it is widely recognized that placebos can have an effect on BP.

In these trials, placebos have almost always been given before the active drug; the present study will compare conditions in which placebo precedes vs. follows the active drug. The effects of placebo treatment will be compared with a standard blood pressure medication (Bisoprolol plus hydrochlorothiazide) in patients with blood pressure that is in the high-normal or mildly hypertensive range (systolic blood pressure between 135 and 150 mmHg). Blood pressure will be monitored in three ways: traditional clinic measurements, self (home) monitoring, and 24 hour ambulatory monitoring.

There will be four periods of approximately 4 weeks each. During the first, patients will monitor their blood pressure at home, and will continue to do this throughout the course of the study. During the second period, they will be randomly allocated to one of the three groups: one that takes initially takes no medication, one that takes placebo, and one that takes the active drug. At this time, when the patients given the placebo will not have already received the active treatment, what we expect to see is that there may be some decrease of the clinic pressure, but not of the home or 24 hour pressure.

During the third 4 week period they will all be taking the active medication, and during the fourth one they will be randomly allocated to have the active medication replaced by either placebo pills or no pills at all. The purpose of this is to test whether there is any conditioning when the placebo is given after the active medication, and to distinguish the placebo effect from the delayed effects of the drug. If this happens, the patients taking the placebo should show a more prolonged reduction of blood pressure than the patients who are taking no capsules during the last period of the study, and we anticipate that this reduction of blood pressure will be seen during the 24 hour monitoring and the home readings.

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