Visual/emotional stimuli and treatment with antidepressants alter Numerical Rating Scale score in patients with chronic pain

Abstract Study objective To examine the impact of visual stimulation (exciting red and tranquilizing green) on the score of the Numerical Rating Scale (NRS) questionnaire in patients with chronic pain. Design Prospective randomized study. Setting Outpatient pain clinic of a university hospital. Patients Two hundred outpatients with chronic pain. Interventions Patients were randomly assigned to receive the NRS questionnaire printed on either red paper (red group) or green paper (green group). Measurements The questionnaire included 5 questions consisting of the NRS in the worst, in the least, and in the average pain during last week and the NRS at rest and on movement at present. Calculation of the sample size was based on power of 0.8 and α = .01. Main results The NRS scores were not different between the 2 groups. In patients on antidepressants (n = 76) and with depression (n = 49), the NRS scores, except the NRS in the worst pain during last week score in patients on antidepressants, were significantly higher in the red group than in the green group (all P ≤ .040). In the red group, the NRS scores were significantly higher in patients with than without depression (all P ≤.003), whereas there was no difference in the scores between patients of the green group with and without depression. Conclusion Our findings suggest that visual/emotional stimuli and treatment with antidepressants alter the NRS score in patients with chronic pain.