title: Annual longitudinal survey at up to five time points reveals reciprocal effects of bedtime delay and depression/anxiety in adolescents.
abstract: OBJECTIVE
  To investigate the longitudinal relationship between sleep habits and mental health in adolescents.
  
  
  METHODS
  Multipoint observation data of up to five years were employed from a prospective cohort study of sleep habits and mental health status conducted from 2009 to 2013 in a unified junior and senior high school (grades 7-12) in Tokyo, Japan. A total of 1078 students answered a self-report questionnaire, including items on usual bed and wake-up times on school days, and the Japanese version of the 12-item General Health Questionnaire (GHQ-12).
  
  
  RESULTS
  Latent growth model (LGM) analysis, which requires three or more time point data, showed that longitudinal changes in bedtime and GHQ-12 score (or score for depression/anxiety) were significantly and moderately correlated (correlation coefficient = 0.510, p < 0.05). Another result of interest was that, using an autoregressive cross-lagged (ARCL) model, bedtime and the depression/anxiety score had reciprocal effects the following year: ie, bedtime significantly affects the following year's depression/anxiety, and vice versa. In addition, the analysis provided estimates of mutually predicted changes: one-hour bedtime delay may worsen the GHQ-12 score by 0.2 points, and one-point worsening of the score may delay bedtime by 2.2 minutes.
  
  
  CONCLUSIONS
  By using up to five multiple time point data, the present study confirms the correlational and reciprocally longitudinal relationship between bedtime delay and mental health status in Japanese adolescents. The results indicate that preventing late bedtime may have a significant effect on improving mental health in adolescents.
authors: Department of Neuropsychiatry, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi, Tokyo 173-0003, Japan.
authors: Mamoru
authors: M
authors: Tochigi
authors: Faculty of Human Sciences, Department of Psychology, University of Tsukuba, 1-1-1 Ten-nodai, Ibaraki, Tsukuba 305-8572, Japan.
authors: Satoshi
authors: S
authors: Usami
authors: Department of Physical and Health Education, Graduate School of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors: Misato
authors: M
authors: Matamura
authors: Department of Physical and Health Education, Graduate School of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors: Yuko
authors: Y
authors: Kitagawa
authors: The University of Tokyo Secondary School attached to the Faculty of Education, 1-15-1 Minamidai, Nakano, Tokyo 164-0014, Japan.
authors: Masako
authors: M
authors: Fukushima
authors: The University of Tokyo Secondary School attached to the Faculty of Education, 1-15-1 Minamidai, Nakano, Tokyo 164-0014, Japan.
authors: Hiromi
authors: H
authors: Yonehara
authors: Department of Physical and Health Education, Graduate School of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan.
authors: Fumiharu
authors: F
authors: Togo
authors: Department of Psychiatry and Behavioral Science, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya, Tokyo 156-8506, Japan.
authors: Atsushi
authors: A
authors: Nishida
authors: Department of Physical and Health Education, Graduate School of Education, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan. Electronic address: psytokyo@yahoo.co.jp.
authors: Tsukasa
authors: T
authors: Sasaki
mesh_terms: D000293:Adolescent; D001007:Anxiety / Q000209:etiology*; D003863:Depression / Q000209:etiology*; D005260:Female; D006184:Habits; D006801:Humans; D007564:Japan; D008019:Life Style; D008137:Longitudinal Studies; D008297:Male; D057566:Self Report; D012892:Sleep Deprivation / Q000523:psychology*; D011795:Surveys and Questionnaires
keywords: Anxiety; Bedtime; Depression; Sleep time; The 12-item General Health Questionnaire (GHQ-12); Wake-up time