Individual differences in pain and placebo analgesia : the role of fear.

Abstract

The title of the PhD thesis is “Individual differences in pain and placebo analgesia – the role of fear”. Placebo analgesia refers to the reduction in pain after the administration of an inert treatment with the information that pain will be reduced. Pain reduction is therefore not attributable to the treatment, but to the conscious belief or expectation that the treatment is effective. However, not everyone responds to placebo medication. The papers presented in this thesis target an (until now) overlooked issue, namely, what characterizes those who do not respond to placebo treatment.

The main hypothesis proposed here is that fear reduces the effectiveness of a placebo intervention on pain. The thesis describes three experiments with a similar structure. Fear was measured by the Fear of Pain Questionnaire and used as a predictor in all studies. In Study III fear was induced experimentally by the anticipation of electric shocks. Pain was induced by thermal heat and rated subjectively (all studies) as well as measured by electrical responses in the brain (Study II). All studies included a Control condition and a Placebo condition. Study III also included a Placebo + Fear condition. This allowed for the causal investigation of the effect of induced fear on placebo analgesia. Placebo effects were found on verbally reported pain and on electrical brain responses. Fear, as measured by questionnaires or as induced experimentally, reduced these effects, thus confirming our main hypothesis in all three studies.