Prediction of placebo responses: a systematic review of the literature

Abstract

Objective: Predicting who responds to placebo treatment-and under which circumstances-has been a question of interest and investigation for generations. However, the literature is disparate and inconclusive. This review aims to identify publications that provide high quality data on the topic of placebo response (PR) prediction. Methods:To identify studies concerned with PR prediction, independent searches were performed in an expert database (for all symptom modalities) and in PubMed (for pain only). Articles were selected when (a) they assessed putative predictors prior to placebo treatment and (b) an adequate control group was included when the associations of predictors and PRs were analyzed.Results: Twenty studies were identified, most with pain as dependent variable. Most predictors of PRs were psychological constructs related to actions, expected outcomes and the emotional valence attached to these events (goal-seeking, self-efficacy/-esteem, locus of control, optimism). Other predictors involved behavioral control (desire for control, eating restraint), personality variables (fun seeking, sensation seeking, neuroticism), or biological markers (sex, a single nucleotide polymorphism related to dopamine metabolism). Finally, suggestibility and beliefs in expectation biases, body consciousness, and baseline symptom severity were found to be predictive. Conclusions:While results are heterogeneous, some congruence of predictors can be identified. PRs mainly appear to be moderated by expectations of how the symptom might change after treatment, or expectations of how symptom repetition can be coped with. It is suggested to include the listed constructs in future research. Furthermore, a closer look at variables moderating symptom change in control groups seems warranted.

Placebo effects and their determinants in gastrointestinal disorders

“…Although some studies indicate a personality characteristic (for example, anxiety) to be associated with a higher placebo response in specific experimental and clinical settings, for example, in motion sickness and pain, 120 poor evidence has been collected that this association is true across all conditions tested. Certainly, a strong publication bias is present, as most investigators use a large battery of psychometric tests and usually report only those that were found to be linked to the placebo response and statistically nonsignificant results are often not published.…”

Placebo‐like analgesia via response imagery

“…due to previous experiences) and different types of pain (e.g. acute vs. chronic pain) (Horing et al., 2014; Peerdeman et al., 2016). Furthermore, participants received standardized and detailed instructions for the imagery exercise.…”

Placebo effects in psychiatry: mediators and moderators

“…In 2014, we published a review 85 screening the respective literature on personality and placebo response and found 21 studies, most with pain as the dependent variable. Most predictors of the placebo response were psychological constructs related to actions, expected outcomes, and the emotional valence attached to these events (eg, goal seeking, self-efficacy or self-esteem, locus of control, and optimism).…”