Melatonin is a hormone secreted from the pineal gland located in the brain. Tryptophan, which is an amino acid, converts into serotonin. Serotonin then converts into melatonin. Serotonin is a neurotransmitter associated with depression.
In addition to improving sleep, melatonin is a strong antioxidant good for the immune system. As we age, melatonin, DHEA, and human growth hormone decline.
The pineal gland controls our 24-hour clock known as our circadian rhythm. In addition to aging, stress and anxiety play a big roll in throwing our clock off. Over production of hydrocortisone will inhibit secretion of melatonin. So treating the adrenals in addition to melatonin is equally important.
As with all my other articles, clinical dosages are what we need. Usually only .5 to max 3 mg is all we need. Just enough to assist our bodies to secrete melatonin on its own again.
When going through stressful times, I always take 500 mg. of magnesium with my melatonin before bedtime. Magnesium will block hydrocortisone and allow the melatonin to work.   If you experience drowsiness the next day, cut down your milligrams of melatonin.