title: Sleep duration and its association with sleepiness and depression in "ronin-sei" preparatory school students.
abstract: OBJECTIVE
  The Japanese word "ronin-sei" refers to a student who has failed their university entrance examination and is preparing to re-take the examination in the following year. We aimed to determine how sleep duration is associated with daytime sleepiness or depression in ronin-sei because impaired daytime performance is known to result from sleep deprivation.
  
  
  METHODS
  The participants in this cross-sectional study were 1075 ronin-sei and 285 university students. Sleepiness and depressive symptoms were assessed using the Epworth Sleepiness Scale (ESS) and the Center for Epidemiologic Studies Depression Scale (CES-D), respectively.
  
  
  RESULTS
  Ronin-sei had significantly shorter sleep duration and earlier bed- and rise-times than university students. There was no significant difference in CES-D between the groups; however, the ESS score of university students was significantly higher than that of ronin-sei. Ronin-sei who slept for 5 to <6h had higher ESS scores than those who slept for 6 to <7h. The mean CES-D score in ronin-sei who slept <5h was significantly higher than in those who slept for 5 to <6h, from 6 to <7h, and from 7 to <8h. Ronin-sei who slept for more than 8h also had higher depression scores.
  
  
  CONCLUSIONS
  Sleep deprivation appears to be common among ronin-sei. Furthermore, a U-shaped relationship was found between sleep duration and depressive symptoms, revealing that ronin-sei who had too little or too much sleep were more likely to exhibit an increase in depressive symptoms.
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan. Electronic address: matsushita@fc.kuh.kumamoto-u.ac.jp.
authors.forename: Masateru
authors.initials: M
authors.lastname: Matsushita
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Koyama
authors.affiliation: Department of Child and Adolescent Psychiatry, Kohnodai Hospital, National Center for Global Health and Medicine, Ichikawa, Chiba, Japan.
authors.forename: Hirokage
authors.initials: H
authors.lastname: Ushijima
authors.affiliation: Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; Osaka University Health Care Center, Toyonaka, Osaka, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Mikami
authors.affiliation: Department of Child Studies, Faculty of Human Life Studies, University of Niigata Prefecture, Niigata, Niigata, Japan.
authors.forename: Yotaro
authors.initials: Y
authors.lastname: Katsumata
authors.affiliation: Kumamoto University Health Care Center, Kumamoto, Kumamoto, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Kikuchi
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Ichimi
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Jono
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
authors.forename: Noboru
authors.initials: N
authors.lastname: Fujise
authors.affiliation: Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Ikeda
mesh_terms: D000293:Adolescent; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis* / Q000523:psychology; D005221:Fatigue / Q000175:diagnosis* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008603:Mental Health; D012890:Sleep / Q000502:physiology*; D012892:Sleep Deprivation / Q000175:diagnosis* / Q000523:psychology; D013334:Students; D011795:Surveys and Questionnaires
keywords: Adolescence; Mental health; Preparatory school; Sleep hygiene