Psychometric properties of the Diurnal Insomnia Symptoms Response Scale (DISRS) in a Mexican population sample APPENDIX

Introduction. Increased rumination is associated with longer night-time sleep onset latency and poorer sleep quality and efficiency in people with insomnia symptoms. Objective. To validate the Diurnal Insomnia Symptoms Response Scale (DISRS) in a general population sample. Method. 102 participants (women = 67 and men = 35) comprising patients and relatives who attended an outpatient consultation at a health center in Mexico City were evaluated. The English-Spanish-English translation system was used by two Spanish-speaking experts on the subject, an independent bilingual expert translated the new version of the scale into English, which was then compared with the original. The following self-administered questionnaires were used to evaluate the convergent, discriminant validity of this tool: the Ruminative Response Scale (RRS), the Insomnia Severity Index (ISI), and Penn State Worry Questionnaire (PSWQ). Results. The internal consistency of the scale items was α = .93. Principal components factor analysis yielded three factors with an eigenvalue of greater than one, which together explain 59.5% of the variance. Correlations between the total DISRS score and the cognitive-motivational dimensions (r = .938, p () .01), negative state (r = .898, p () .01) and tiredness (r = .853, p () .01) were statistically significant. Insomnia symptoms (SCC = .89) outweighed worries (SCC = .33) and ruminant responses (SCC = .33) when discriminating between cases with low and high levels of rumination associated with insomnia symptoms. Discussion and conclusion. Our results suggest that the DISRS scale has adequate psychometric properties that make it valid and reliable for use with the Mexican population.