A test of psychological and electrodermal changes immediately after the delivery of 3 analgesic treatment messages

INTRODUCTION: Placebo analgesia often results when a pain reduction treatment message is delivered to a patient or research participant. Little information exists regarding the psychological changes that are immediately triggered by the delivery of a treatment message. OBJECTIVES: This experiment tested the impact of 3 different analgesic treatment messages on the expectations, feelings, and electrodermal activity of participants anticipating a pain stimulus. METHODS: In laboratory sessions, healthy participants (N = 138) were randomly assigned to 1 of 4 conditions in a between-subject design. The design included a no treatment message control condition and 3 treatment message conditions: a standard analgesic message, an analgesic treatment with side-effect message, and a double-blind analgesic message. After the treatment message manipulation, measures were taken of: treatment efficacy expectations, pain experience expectations, pretask anxiety, positive affect, negative affect, and electrodermal activity. RESULTS: Overall, the dependent measures showed relatively few correlations. Furthermore, across all 3 message conditions, treatment-specific expectations were greatly increased compared with the control condition. Finally, participants in the double-blind message condition displayed elevated negative affect. CONCLUSION: All 3 analgesic treatment messages produced a stronger immediate influence on treatment efficacy expectations than on the other dependent measures. Treatment messages can alter negative affect along with expectancies. The low correlations found between dependent measures suggest that different patterns of psychological responses may emerge from analgesic treatment messages depending on contextual factors.