Topic: Placebo
Title: The time component of expectation in placebo analgesia and nocebo hyperalgesia
Eleonora Maria Camerone 1, Alessandro Piedimonte 2, Marco Testa 1,  
Fabrizio Benedetti 2,  Elisa Carlino 2.

1Department of Neuroscience, Rehabilitation, Ophthalmology, Genetics  
and Maternal and Child Science (DINOGMI), University of Genoa

2 Department of Neuroscience, University of Turin Medical School,  
10125, Turin

Background and aims
The time component of expectations underlying placebo analgesia and nocebo hyperalgesia,  was not yet investigated. This study assesses whether manipulation of temporal information associated with placebo/nocebo cream treatments, modulates cream onset of action.
Methods
160 healthy volunteers underwent the same electric shock pain paradigm at baseline, after 10, 20 and 35 minutes. An inert cream was applied after the baseline trial. In the placebo condition, all participants were told that the cream had strong analgesic properties, but some were told that it would be effective in 5 minutes (Exp 5), others in 15 (Exp 15), and others in 30 minutes (Exp 30). The nocebo condition was identical, but volunteers were told that the cream had powerful hyperalgesic properties. Control and natural history groups were also present. Pain perception was assessed by means of Numeric Rating Scale (NRS).
Results
The onset of placebo/nocebo cream analgesia and hyperalgesia varied accordingly with the given temporal suggestions. Significant analgesic (placebo) and hyperalgesic (nocebo) responses were present after 10 minutes from cream application in Group Exp 5 (p<.05). Differently, in Group Exp 15, there was no significant pain reduction/pain increase in the trial after 10 minutes, but only in the trial after 20 minutes as well as in Group Exp 30, pain reduction/pain increase occurred after 35 minutes (p<.05).
Conclusions
These findings show that the time component of expectation is finely tuned with the onset of placebo analgesia and nocebo hyperalgesia.

06 - THE TIME COMPONENT OF EXPECTATION IN PLACEBO ANALGESIA AND NOCEBO HYPERALGESIA