title: 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 < .01). Multiple regression analysis revealed that the scores of both nightmares and insomnia were significantly associated with the increase in depression score (nightmares (β = 0.09, P < .01); insomnia (β = 0.39, P < .01)). Participants with coexisting nightmares and insomnia showed higher depression scores than participants with insomnia alone or those with nightmares who did not have insomnia (P < .01).
  
  
  CONCLUSIONS
  Insomnia and nightmares independently and additively impact the aggravation of depression.
authors.affiliation: Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan; Yoyogi Sleep Disorder Center, Tokyo, Japan.
authors.forename: Shun
authors.initials: S
authors.lastname: Nakajima
authors.affiliation: Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan; Yoyogi Sleep Disorder Center, Tokyo, Japan. Electronic address: inoue@somnology.com.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Inoue
authors.affiliation: Department of Somnology, Tokyo Medical University, Tokyo, Japan.
authors.forename: Taeko
authors.initials: T
authors.lastname: Sasai
authors.affiliation: Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan; Yoyogi Sleep Disorder Center, Tokyo, Japan.
authors.forename: Isa
authors.initials: I
authors.lastname: Okajima
authors.affiliation: Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan; Yoyogi Sleep Disorder Center, Tokyo, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Komada
authors.affiliation: Department of Neurology, Institute of the Neurological Sciences, Tottori University Faculty of Medicine, Tottori, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nomura
authors.affiliation: Japan Foundation for Neuroscience and Mental Health, Tokyo, Japan.
authors.forename: Kiyohisa
authors.initials: K
authors.lastname: Takahashi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology* / Q000209:etiology; D004325:Dreams / Q000523:psychology*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D020184:Night Terrors / Q000150:complications / Q000453:epidemiology / Q000523:psychology; D011569:Psychiatric Status Rating Scales; D012424:Rural Population / Q000706:statistics & numerical data; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications / Q000453:epidemiology* / Q000523:psychology; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Comorbid; Depression; Dream; Insomnia; Nightmare; Sleep