Evidence points to a possible association between optimism and the placebo response

The influence of personality traits on the placebo/nocebo response: A systematic review. Alexandra Kern et al. Journal of Psychosomatic Research, November 7 2019, 109866. https://doi.org/10.1016/j.jpsychores.2019.109866

Highlights
• Results on the influence of personality traits on placebo responses are heterogeneous.
• More studies are available on the influence of personality traits on the placebo response than on the nocebo response.
• Optimism seems to be positively associated with placebo responses.
• Anxiety might lead to increased nocebo responses.

Abstract
Objective: Some people might be more prone to placebo and nocebo responses than others depending on their personality traits. We aimed to provide a systematic review on the influence of personality traits on placebo and nocebo responses in controlled and uncontrolled studies.

Methods: We conducted a systematic literature search in the databases CINAHL, AMED, PsycINFO and EMBASE for relevant publications published between January 1997 and March 2018. For all included papers, we conducted an additional forward search.

Results: After screening 407 references, we identified 24 studies. The Big Five (i.e., neuroticism, extraversion, openness to experience, agreeableness and conscientiousness) and optimism were the most frequently investigated personality traits. Several studies found a positive association between optimism and the placebo response. Furthermore, we found that higher anxiety was associated with increased nocebo responses.

Conclusion: Evidence points to a possible association between optimism and the placebo response. Therefore, further emphasising the investigation of the influence of optimism on the placebo/nocebo response seems warranted. For clinical practice, the impact of anxiety on the nocebo response might be important to identify patients who might be more prone to experiencing side effects of medical treatments.

Keywords: Nocebo responsePersonalityPlacebo responseSystematic review