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Asian J Psychiatr. 2014 Jun;9:61-6. doi: 10.1016/j.ajp.2014.01.006. Epub 2014 Jan 29.

Sleep duration and its association with sleepiness and depression in "ronin-sei" preparatory school students.

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Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan. Electronic address:
Department of Neuropsychiatry, Faculty of Life Sciences, Kumamoto University, Kumamoto, Kumamoto, Japan.
Department of Child and Adolescent Psychiatry, Kohnodai Hospital, National Center for Global Health and Medicine, Ichikawa, Chiba, Japan.
Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; Osaka University Health Care Center, Toyonaka, Osaka, Japan.
Department of Child Studies, Faculty of Human Life Studies, University of Niigata Prefecture, Niigata, Niigata, Japan.
Kumamoto University Health Care Center, Kumamoto, Kumamoto, Japan.



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.


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.


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.


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.


Adolescence; Mental health; Preparatory school; Sleep hygiene

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