title: Actigraphic predictors of the depressive state in students with no psychiatric disorders.
abstract: BACKGROUND
  Insomnia is one of the characteristics of the early depressive state. One-third of university students has a mild depressive state. In this study, we examined whether the depressive state would be correlated with the actigraphic-derived daytime activity levels (DAL) and total sleep time (TST) in students with no psychiatric disorders.
  
  
  METHODS
  Consenting volunteers were monitored at home for 3-4 days with a wrist actigraph. The DALs for 3 h before noon (DAL-M) and after 13:00 h (DAL-A) were calculated. The states of sleep and wakefulness were judged based on the activity levels, using a special algorithm. On the first day of the recording, the subjects were requested to fill a questionnaire, "Center of Epidemiologic Scale for Depression Scale (CES-D)," to evaluate the severity of their depressive state.
  
  
  RESULTS
  There was a significant correlation between the DAL-M and DAL-A in both males (r=0.52, n=27) and females (r=0.50, n=21). TST was significantly correlated with depressive state only in the females (r=-0.49, n=28). In contrast, there was no significant correlation between the DAL and the severity of the depressive state. By multiple regression analysis, TST was only a good predictor of depressive state.
  
  
  CONCLUSIONS
  The results of this investigation suggest that TST could be used as an index of the depressive state. The TST values in this study decreased as the severity of the depressive state increased, which suggests an association between the severity of the depressive state and insufficient sleep.
authors.affiliation: Department of Hygiene and Public Health, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-Ku, Tokyo 113-8602, Japan. kawada@nms.ac.jp
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kawada
authors.forename: Masao
authors.initials: M
authors.lastname: Katsumata
authors.forename: Hiroko
authors.initials: H
authors.lastname: Suzuki
authors.forename: Takako
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D000204:Activity Cycles; D000328:Adult; D003863:Depression / Q000503:physiopathology*; D003866:Depressive Disorder / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic; D009043:Motor Activity; D011569:Psychiatric Status Rating Scales; D012890:Sleep / Q000502:physiology*; D013334:Students; D014851:Wakefulness / Q000502:physiology