[Sleep habits and its relation to depression].

There have been a lot of studies on the relationship between insomnia and depression, however, only a little is elucidated about the relationship between sleep habits and depression. In modern societies, long working hours, shift-work, and late bed-time are quite prevalent. However, based on the findings of a few recent papers, it is suggested that long working hours, shift work, heavy internet use, eveningness and late bed-time are associated with short sleep duration and/or insomnia. Then, short sleep duration and/or insomnia would contribute to developing depression. So, as is in the case of metabolic syndrome or hypertension, depression would be a life-style related disease.