Computational protocol: Nocebo hyperalgesia: contributions of social observation and body-related cognitive styles

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Protocol publication

[…] Participants were recruited via newspaper and billboard advertisements. Differences in pain sensitivity between healthy men and women have been replicated in numerous studies, which showed that experimenter sex influenced pain reports, and that the sex of the model and participants influenced socially induced nocebo effects. Therefore, we kept these factors constant by employing a female model and including only women in our study. For the power analysis, we used the effect size of partial η2=0.09 found for the interaction in our last paper as an approximation. We converted it via G*Power to the effect size f (V)=0.31. A minimum total sample size of N=82 participants was required to detect an interaction effect of that size (α=0.05 and power =0.80). Since, in our last study, participants had to be excluded, we decided to recruit more participants than the minimum required. A total of 109 healthy, right-handed women were randomly assigned to one of the two conditions. Twelve women were excluded after testing but before data analyses, as they reported suffering from depression (four), anorexia nervosa (one), anxiety disorders (two), agoraphobia (one), arthrosis (one), chronic back pain (one), fibromyalgia (one), and craniomandibular dysfunction (one). The remaining 97 participants (mean age nocebo condition [NC] 41.3±15.5 years, mean age control condition [CC] 44.7±15.5 years) were included in the analysis. The groups did not differ with regard to age (). [...] Differences regarding age, depression, anxiety, pain catastrophizing, unspecific somatic complaints, hypochondriacal concerns, and the credibility ratings between the participants in the two conditions were compared with independent t-tests.Prior tests showed that the assumptions for a 2×2 repeated measures analysis of variance (ANOVA) were fulfilled: the data were normally distributed (Kolmogorov–Smirnov test) and variances were homogeneous (Levene’s test). In order to test the interaction hypothesis for the nocebo effect, the mean pain intensity score for each hand was calculated, and a 2×2 repeated measures ANOVA with between-subject factor condition (NC/CC) and within-subject factor application of ointment (yes/no) was computed. Planned contrasts were calculated using independent or paired t-tests as appropriate. As measures of effect sizes, η2 and Cohen’s d were calculated.The nocebo response for each individual participant was determined by the difference between the mean pain intensity ratings with and without ointment for that participant. Higher values indicated a stronger nocebo response.Pearson correlations were computed for each condition for the nocebo response with empathy, pain catastrophizing, unspecific somatic complaints, and hypochondriacal concerns. The level of significance was set at P<0.05. All analyses were carried out with STATISTICA for Windows software, version 10 (StatSoft Inc., Tulsa, OK, USA). […]

Pipeline specifications

Software tools G*Power, Statistica
Application Miscellaneous
Organisms Homo sapiens