The nocebo (or negative
placebo) effect is an under-researched phenomenon with serious clinical
implications. Research has shown an inverse relationship between nocebo
responding and optimism, affected by situational variables. This study
examined how biofeedback affects this relationship. Thirty-three
undergraduates were randomly assigned to one of four conditions in a 2x2
design [Group variables: nocebo instructions (pill affecting heart rate/ inactive)
and biofeedback (present/absent)]. Optimism was measured by the LOT-R and response
by change in HRV. Mixed between-within ANOVAs revealed no significant effects on
HRV for nocebo instructions or biofeedback. Controlling for pre-intervention
HRV, there was a correlation between post-intervention HRV and LOT-R
scores in one group (nocebo instructions present, biofeedback absent:
r1/4.763, p1/4.028, two-tailed). Higher optimism increased nocebo
responding in the simple nocebo condition, contrary to extant researc