Table 1.

Sample demographics, questionnaires scores (mean ± SD).

N	20
Age (y)	22.9 (2.7)
Ethnicity	Caucasian
BMI (kg/m2)	22.1 (2.2)
Anxiety level (BAI)	1.4 (2.2)
Mood (BDI-II)	1.1 (1.9)
Caffeine (cups/day)	0.4 (0.5)
Alcohol (doses/week)	3.2 (3)
Sleep quality (PSQI)	3.8 (0.7)
Daytime propensity to fall asleep (ESS)	3.5 (2.9)
Chronotype (HO)	52.9 (5.1)
Sleep time (hh:min, sleep diary)	23:37 (44 min)
Wake time (hh:min, sleep diary)	7:33 (45 min)
Sleep time (hh:min, actigraphy)	23:31 (46 min)
Wake time (hh:min, actigraphy) Average clock time of dim-light melatonin onset (hh:mm)	7:31 (47 min) 21:07 (77 min)

Anxiety was measured by the 21-item Beck Anxiety Inventory (BAI ≤ 14) [33]; mood by the 21-items Beck Depression Inventory II (BDI-II ≤ 14) [34]; sleep quality by the Pittsburgh Sleep Quality Index Questionnaire (PSQI ≤ 7) [35]; daytime propensity to fall asleep in non-stimulating situations by the Epworth Sleepiness Scale (ESS ≤ 11) [36]; chronotype by the Horne-Östberg Questionnaire (<42: evening types; 42–58: intermediate types; >58: morning types) [37].