Inclusion Criteria:  male sex in order to avoid the potential impact of menstrual cycle on sleep physiology or HPA axis activity, age within the range of 18 to 34 years, a body-mass-index below 25, an Epworth Sleepiness Score (ESS) below 10, habitual sleep onset latency below 20 minutes, regular sleep-wake rhythm with bedtime between 11 pm and 1 am, absence of any somatic or psychiatric disorders, no acute or chronic medication intake, non-smoking, no history of drug abuse (lifetime use > 5 occasions, except occasional cannabis use) caffeine consumption of less than 4 units per day (coffee, tea, chocolate, cola, energy drinks)  Exclusion Criteria:  - Failure to meet inclusion criteria