Photo Credit: iStock.com/microgen

The following is a summary of “Generalisation of Placebo and Nocebo Effects: Current Knowledge and Future Directions,” published in the May 2025 issue of European Journal of Pain by Weng et al. 

Placebo and nocebo effects, which influence pain and somatic sensations, remain inadequately understood regarding their generalization across different conditions.  

Researchers conducted a retrospective study to explore the stimulus and response generalization of placebo and nocebo effects on common somatic sensations, including pain, itch, dyspnea, nausea, and fatigue.  

They systematically searched the PubMed, Web of Science, and PsycINFO databases for peer-reviewed articles reporting on experimental studies in humans regarding the induction and generalization of placebo and nocebo effects on prevalent somatic sensations (i.e., pain, itch, dyspnea, nausea, and fatigue).  

The results showed that 23 studies were included from 2025 identified records. These studies demonstrated that placebo and nocebo effects could generalize over stimuli (at perceptual, categorical, and treatment levels) and responses within modalities. Most studies focused on pain, while fewer examined itch, dyspnea, nausea, and fatigue. Generalization effects were larger when the generalization stimuli and responses closely resembled the initial ones. Placebo or nocebo effects were more likely to generalize when both verbal suggestion and conditioning were used, compared to when only 1 was applied. Response generalisation across modalities remained unclear.  

Investigators concluded that placebo and nocebo effects were capable of generalizing across stimuli and responses, and further experimental and clinical research was necessary to investigate the carryover effects of these phenomena. 

Source: onlinelibrary.wiley.com/doi/10.1002/ejp.70018