Demographic and sleep characteristics, self-ratings (mean, standard deviation (SD)) of early (EC), intermediate (IC) and late chronotypes (LC).

Abbreviations: PSQI, Pittsburgh Sleep Quality Inventory ESS, Epworth Sleepiness Scale KSS, Karolinska Sleepiness Scale BDI, Beck Depression Inventory. *P < .05 ** P < .01 a expressed in number of school and study years. b expressed in typical number of cigarettes per day. c expressed in typical number of standard alcoholic drinks per week. d sleep/wake cycle two days before the measurement day. e sleep/wake cycle one day before the measurement day. Demographic and sleep characteristics, self-ratings (mean, standard deviation (SD)) of early (EC), intermediate (IC) and late chronotypes (LC).