Impact of frequency of nightmares comorbid with insomnia on depression in Japanese rural community residents: a cross-sectional study

Abstract Objective Nightmares and insomnia are known to be associated with the development and aggravation of depression. Our community-based study was conducted to clarify the relation between the impacts of nightmares and insomnia on depression. Methods A cross-sectional questionnaire-based survey was administered to residents of a rural community in Japan. In all, 2822 participants responded to questions assessing personal characteristics, the Pittsburgh Sleep Quality Index (PSQI) for assessing insomnia, and a 12-item version of the Center for Epidemiological Studies Depression scale (CES-D) for evaluating depression. Nightmare frequency was assessed using an item for nightmares on the PSQI. Results Nightmares more frequently occurred in participants with insomnia than those without ( P β =0.09, P β =0.39, P P Conclusions Insomnia and nightmares independently and additively impact the aggravation of depression.