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http://clinicaltrials.gov/show/NCT01152580 If you want to know more about melatonin's other benefits, amazon have books on it.
Those who don't want to supplement with melatonin-
Sleep in a dark room, because light disrupts melatonin production. If there are light sources you can't control, you might consider wearing a sleep mask.
Make sure you get at least seven full hours of sleep.
“Power down†before bedtime. Try to turn off the computer and the television at least an hour before you turn in.
Get regular exercise. One study found that an hour on a stationary bicycle could increase melatonin levels up to three times.5 This is just an example; it doesn't mean you need to use an exercise bicycle – it just points up the value of exercise in melatonin production.5
Meditate or do some form of deep relaxation before you go to bed. A study found that a period of meditation greatly increased night-time plasma melatonin levels.6
Get some sun during the day. Sunlight inhibits melatonin production, so getting sun exposure during daylight hours gives your pineal gland (which produces the melatonin) a rest so it can spring into action at night.
Try to eat foods that contain melatonin. Mustard seeds, alfalfa and sunflower seeds, fennel seeds, and lemon verbena all contain a good amount of melatonin. Oats, tomatoes, corn, and barley, also contain melatonin, but not as much.