Effects of Hydrocortisone, Melatonin, and Placebo on Jet Lag

This study will examine the effects of cortisol (hydrocortisone), melatonin, a combination of cortisol and melatonin, and placebo (an inactive substance) on jet lag symptoms. Jet lag is a term used to describe symptoms people commonly experience after rapid travel across several time zones. The cause of jet lag is not known, but various hormones, including cortisol and melatonin, have a day-to-night pattern of secretion and play a role in maintaining the body's internal rhythms. This study will test whether taking cortisol, melatonin, or both can help re-establish the body's day-night cycle and result in less jet lag. People between 18 and 65 years of age who are planning a non-stop eastward flight with the following characteristics may be eligible for this study: * Crossing six to eight time zones (6 to 8 hours difference between Eastern Standard Time and the destination) * Destination between 30 and 50 latitudes (approximately Cairo to London) * Evening flight (5 PM to midnight) with morning arrival * Remaining abroad at least 4-10 days Candidates must have a body mass index (BMI) between 20 and 30 kg/M (not too thin and not overweight) and must not be taking medicines that affect sleep or cortisol or melatonin levels. Prospective participants are screened with a medical history, blood tests, and check of blood pressure, height, and weight. Pre-flight Procedures Participants keep a sleep journal 3 days before the flight. For 1 day within 3 days of the flight they fill out jet lag and sleepiness questionnaires and collect morning and bedtime saliva samples for measurement of cortisol and melatonin. The saliva is collected by chewing on two small cotton pads and spitting them into a tube. Premenopausal women provide a urine sample the week before the flight to test for pregnancy. On the day of the flight, the participants do not collect saliva or fill out sleep logs or questionnaires. They are given two bottles with study medication. One bottle, labeled "AM," c