Do we need to deceive to achieve within placebo analgesia: How does personality influence open-label placebo and deceptive placebo responding?

Objective: Research has suggested open-label placebos are effective, however, there is a lack of research comparing the effectiveness of an open-label placebo (OLP) with a deceptive placebo (DP), although one study did find an OLP and DP were equally as effective for reducing pain. Furthermore, there is a gap within the literature investigating the influence of personality within OLP responding. This study aimed to compare the effectiveness of an OLP to a DP and investigated the role of personality within OLP analgesia.

Method: 75 participants were allocated to one of three groups; OLP (n = 25), DP (n = 26) and no-treatment (NT; n = 24). All participants completed a baseline cold pressor test (CPT) and measures of pain tolerance and pain intensity. Participants in the OLP group were informed they were receiving a placebo and participants in the DP group were informed they were receiving a painkiller. Those in the OLP and DP groups then received a placebo nasal spray, with the NT group receiving no placebo. All participants then completed a second CPT and the pain measures. Several personality-related variables were also measured.

Results: A one-way ANCOVA revealed no significant differences between groups for pain tolerance, F(2, 71) = 1.903, p = .157. However, significant differences were revealed between groups for self-reported pain intensity, F(2, 71) = 4.838, p = .011, η2 = .120. Planned contrasts revealed that receiving an OLP and a DP significantly decreased pain intensity compared to the NT group, with no significant differences between the effectiveness of the OLP and the DP. Exploratory analysis, using moderated regression analysis, revealed fear of minor pain was positively associated with placebo analgesia within the OLP group. Fear of medical pain was positively associated with pain intensity for those in the OLP group, however, there was a negative association for those in the DP group. There was a positive association between pain intensity and agreeableness for those in the DP group, however, a negative association for those in the OLP group.

Conclusion: An OLP and a DP were both effective for reducing subjective pain intensity, although there were no significant differences between OLP and DP effectiveness. This suggests the use of deception within placebo analgesia should be questioned with healthy participants, as placebos given openly remained as effective as placebos given deceptively. This was also the first study to highlight that agreeableness, fear of minor pain, and fear of medical pain moderated OLP analgesia in a differing direction to DP analgesia.