Physiological, Cognitive, and Personal Features in the Link Between Placebo-effect and Variability of Pain Reports

Physiological, Cognitive, and Personal Features in the Link Between Placebo-effect and Variability of Pain Reports

Exploring the Role of Physiological, Cognitive, and Personal Features in the Link Between Placebo-effect and Variability of Pain Reports

This study attempt to identify whether and how factors known or considered to be related with analgesic placebo effect or variability of pain reports separately, may contribute to their coupling. Among these factors - personal traits such as optimism, focus of attention, suggestibility, and short-term memory along with characteristics of stress and relaxation. Additionally, the role of pain sensitivity and the individual's pain modulation profile in the relationship between analgesic placebo effect and variability of pain reports will be examined.

Data will be collected from 130 patients with non-specific chronic back pain that will be recruited for a prospective cross-sectional study. To characterize the main study variables, the participants will undergo the Focused analgesia selection test (FAST) which evaluates within-subjects variability of pain reports, and placebo manipulation containing administration of an inert injection accompanied by a verbal suggestion, which is expected to produce placebo effects. The involvement of additional factors considered associated with the within-subjects variability of pain reports and the placebo response will be explored. Stress and well-being characteristics will be examined by measuring cortisol levels in saliva and in hair, salivary level of Secretory Immune globulin A (SIgA), and an autonomic nervous system function and a stress perception questionnaire. Personal traits such as suggestibility, optimism, and Focus of attention, will be examined using questionnaires. Memory will be assessed by memory task, and factors related to the pain modulation system will be examined using psychophysical tests, and a pain sensitivity questionnaire.

The reduction in pain intensity on the 0-100 numerical rating scale (NRS) after normal saline injection

The variance of within person pain scores reported on a 0-100 Visual Analog Scale VAS during 7 days via pain-dairy at baseline

Experimental paradigm which allow calculation of within-subjects variability of pain reports in response to thermal stimuli

Change in pain intensity on the 0-100 numerical rating scale (NRS) in response to the first and last electrical noxious stimuli

Change in pain intensity on the 0-100 numerical rating scale (NRS) in response to concurrent noxious stimuli

Inclusion Criteria: Literate adults Aged 18 - 80 years A diagnosis of chronic back pain Sufferings from back pain during the last 3 months or more, with an intensity of 3 or more on a 0-10 NRS Exclusion Criteria: Mental retardation or cognitive impairment Pregnancy or breast-feeding Malignancy and a diagnosis of malignant disease