Melatonin is a hormone secreted by the pineal gland, a pea-sized gland at the base of the brain. The exact function of melatonin is still poorly understood, but it is critically involved in regulating the body's circadian rhythms "the natural biorhythm of hormone secretion" as well as the sleep/wake cycle. Release of melatonin is stimulated by darkness and suppressed by light. It appears that some people may under-produce melatonin at night when it is needed, and over-produce it during the day when it should be low.
 
Seasonal affective disorder (SAD) is associated with progressive winter depression as the days get shorter. Typically, these individuals feel depressed, slow down, and generally oversleep, overeat, crave carbohydrates and women can experience resulting hormone imbalances such as increased PMS symptoms, in the winter. Improvement progresses as days increase in length. In the summer, these same patients feel elated, active, and energetic. A lack of exposure to full-spectrum natural light appears the most logical explanation as it triggers a reduced secretion of melatonin from the pineal gland and an increased secretion of cortisol by the adrenal glands.

Insomnia:

• Use between late afternoon and bedtime.
• Melatonin plays an important role in the induction of sleep.
• Several double-blind trials have shown melatonin supplementation to be very effective in promoting sleep.
• Low melatonin secretion at night are thought to be an extremely common cause of insomnia in the elderly, while in younger individuals this is less of a factor.

• Melatonin may help shift workers adjust to new sleep patterns when shifts are changing. 

• Use during and for 5 days after travel that crosses time lines.
• Several double-blind studies have shown 3 to 5 mg of melatonin to be very effective in relieving jet lag.

• Melatonin supplementation may improve SAD because it not only increases brain melatonin levels, but also because it may suppress cortisol secretion.

Benefits:

• Promotes positive sleep/wake cycles
• Effective in relieving jet lag
• May improve SAD (seasonal affect disorder)
• Helps shift workers adjust to new sleep patterns
• Quickly absorbed and utilized by the body