Optimization of Melatonin Administration in Healthy Adults

The goal of this clinical trial is to evaluate whether the timing and dosage of exogenous melatonin can improve sleep onset and maintenance in healthy adults aged 18-45 years (50% female) with no history of sleep disorders. The main questions it aims to answer is whether an optimized melatonin administration schedule (4 mg, 3 hours before bedtime) will be more effective in improving sleep initiation and maintenance than an administration schedule more commonly advised (2 mg, 30 minutes before bedtime). Researchers will compare five conditions involving different combinations of melatonin or placebo administered 30 minutes or 3 hours before bedtime to see if earlier timing and/or higher dosage produces better sleep outcomes. Participants will: * Complete a habituation night without any intervention. * Undergo five randomized, double-blind experimental sleep conditions including: 2 mg melatonin 30 minutes before bedtime 2 mg melatonin 3 hours before bedtime 4 mg melatonin 30 minutes before bedtime 4 mg melatonin 3 hours before bedtime Placebo at both time points * Be monitored via polysomnography to measure sleep parameters