Epidemiological studies on dreams, sleep habits and mental symptoms in Japanese junior high students aged 12?15 years (2)

Questionnaires on morningness-eveningness by Torsvall and Akerstedt, sleep habits, psychiatric aspects and dreaming were administered to 870 students aged 12–15 years attending one of two junior high schools located in urban area in Kochi city (33°N) and suburban and neighboring area. Students who had negative dreams that were frightening, sad and so on tended to have later bedtimes and a shorter sleep duration and more frequently felt depressed or were unreasonably easily angered than those who had happy dreaming. A later bedtime may be related to a higher frequency of negative dreaming, which seems to trigger mental symptoms such as a depressed mood and irritation in Japanese adolescents.