Retest reliabilities for two single items measuring bad dream frequency (Pittsburgh Sleep Quality Index (PSQI)) or nightmare frequency (Mannheim Dream Questionnaire (MADRE))

Abstract

Several measures eliciting nightmare frequency have been developed over the years. Most of the measures show sufficient reliability, but some studies are based on the four-point item of the Pittsburgh Sleep Quality Index (PSQI) measuring bad dream frequency – even though reliability data for this item have not been published. The present study included a sample of N = 277 participants (wait-list control group of a sleep app study) who completed the PSQI and the nightmare frequency scale of the Mannheim Dream Questionnaire (MADRE) at baseline, at Week 6, and Week 12. Whereas the retest reliability coefficients were sufficiently high for the MADRE nightmare scale, reliability for the PSQI bad dream frequency item was not adequate. Despite the high inter-correlations between different nightmare and bad dream frequency measures, the question of validity is still open to future research, e.g., whether nightmares (with awakening at the end) or disturbing dreams (with or without awakening from the dream) should be the focus of research, especially in the context of investigating model of the nightmare disorder.