Late bedtime: influencing factors and its association with depression and externalizing problems among adolescents

  Objective  To explore influencing factors of late bedtime and associations of late bedtime on weekday/weekend, discrepancy between weekday and weekend bedtime with depression and externalizing problems in adolescents.

  Methods  The data of the study were from the second survey of Adolescent Mental Health in China conducted in 2009. Totally 4 464 adolescents aged 10 – 21 years were selected with stratified multistage cluster random sampling in 9 cities located in north-western, eastern, western and central China for a self-administered on-site questionnaire survey.

  Results  Weekday and weekend late bedtime were reported by 24.3% and 35.9% of the male participants, but by 28.9% and 38.9% of the female participants, with significant differences (P_weekday < 0.001 and P_weekend < 0.05) and suggesting that the female participants were more likely to have late bedtime. Compared to the participants with poor parental relationship, the participants with very good and good parental relationship reported both significantly less weekday and less weekend late bedtime (P_{very good parental relationship} < 0.01, P_{good parental relationship} < 0.05). The average age was 15.07 ± 2.45 and 16.8 ± 2.02 years for the participants reporting weekday and weekend late bedtime, which were significantly different from those not reporting weekday and weekend late bedtime (15.19 ± 2.48 and 16.20 ± 2.35) (both P < 0.001), suggesting that the participants at elder age were more likely to have late bedtime. After adjusting demographic variables, both weekday and weekend late bedtime were positively associated with depression score (β_weekday =0.051, P < 0.01; β_weekend = 0.099, P < 0.001) and with the score for externalizing problems (β_weekday = 0.038, P < 0.05; β_weekend = 0.122, P < 0.001). The discrepancy between weekday and weekend late bedtime was positively correlated with both depression score (β_{weekend-weekday} = 0.097, P < 0.001) and the score for externalizing problems (β_{weekend-weekday} = 0.151, P < 0.001).

  Conclusion  The adolescent being female, at elder age, in a family with poor parental relationship, and being a resident student are more likely to have weekday and weekend bedtime. The adolescents having late bedtime are at a high risk of depression and have externalizing problems.