Association between mental health status and sleep status among adolescents in Japan: A nationwide cross-sectional survey

Objective: Previous epidemiological studies on relationships between mental health status and sleep status of adolescents have not been sufficiently representative. In the present study, using samples representative of Japanese adolescents nationwide, associations between mental health status and various sleep statuses were examined. Method: The survey was conducted in December 2004 and January 2005 among students enrolled in randomly selected junior and senior high schools throughout Japan, using self-administered questionnaires that addressed lifestyle, sleep status, mental health status, and personal data. Of 103,650 questionnaires collected, 99,668 were analyzed. Sleep status was assessed according to sleep duration, subjective sleep assessment, bedtime, and insomnia symptoms. The Japanese version of the 12-item General Health Questionnaire was employed for assessment of mental health status. Results: Mental health status of subjects whose sleep duration was less than 7 hours, and those who slept 9 hours or more, was poorer than that of subjects who slept for 7 hours or more but less than 9 hours. A U-shaped association was observed between mental health status and sleep duration. Furthermore, a linear association was observed between subjective sleep assessment and mental health status; the worse the subjective sleep assessment, the poorer the mental health status. Mental health status was also inversely proportional to the frequency of insomnia symptoms. Conclusion: The fact that sleep duration and subjective sleep assessment showed different patterns of association with mental health status indicates that these 2 sleep parameters have independent significance. Considering these associations, it is important to promote mental health care and sleep hygiene education for adolescents.