Gender and the nocebo response following conditioning and expectancy

Abstract Objective To investigate the role of Pavlovian conditioning and expectancy and of gender on the nocebo effects. Methods Conditioning experiment: Forty-eight healthy male and female volunteers were investigated for 3 days using a standard rotation procedure. Subjects in the experimental group received a salient oral stimulus prior to rotation; subjects in the control group received the stimulus 12 h after rotations on Days 1 and 2; on Day 3, all subjects received the stimulus prior to rotation. Expectancy experiment: Another 48 healthy subjects were rotated 5×1 min once only. All subjects received the same oral stimulus immediately prior to rotation; subjects in the experimental group were told that the symptoms might worsen with the stimulus; controls did not receive additional information. In both experiments, symptom rating (SR) and rotation tolerance (RT) were determined. Results Conditioning significantly reduced RT ( P =.015) and increased SR ( P =.024). For both RT and SR, a significant “day×group×gender” effect was found ( P =.044; SR: P =.011) indicating that conditioning was more effective in women. Expectancies lowered RT ( P =.085) without affecting SR. There was a significant “rotation×gender” interaction on RT ( P =.005) indicating that the expectancy was more effective in men. Conclusion Women responded stronger to conditioning while men responded to expectancies, but to a lesser degree. It needs to be determined whether this is restricted to nausea-specific conditions or can be generalized across clinical and experimental conditions.