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J Psychosom Res. 2005 Feb;58(2):121-7.

Reconsidering the role of personality in placebo effects: dispositional optimism, situational expectations, and the placebo response.

Author information

1
Department of Psychology, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606-3390, USA. ageers@utnet.utoledo.edu

Abstract

OBJECTIVE:

Prior investigations have failed to find reliable personality differences in placebo responding. The present study tests the hypothesis that personality and situational variables interact to determine placebo responding.

METHODS:

Optimists and pessimists were randomly assigned to one of three conditions. In the first condition, the participants were told that they were to ingest a pill that would make them feel unpleasant (deceptive-expectation group). In the second condition, the participants were told that they were to ingest a pill that would make them feel either unpleasant or was an inactive substance (conditional-expectation group). Finally, a third group was told they were to ingest a pill that was inactive (control group).

RESULTS:

Pessimists were more likely than optimists to follow a negative-placebo expectation when given a deceptive expectation, but not when given a conditional expectation.

CONCLUSION:

The personality variable optimism-pessimism relates to placebo responding when individuals are given a deceptive but not a conditional expectation. This suggests that personality and situational variables interact to determine placebo responding.

[Indexed for MEDLINE]

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