Melatonin & Seasonal Affective Disorder

Melatonin is a hormonal brain chemical that is associated with regulating sleep patterns and the human body's circadian rhythm. In recent years, it has been suggested by the medical and psychological community that the overproduction of melatonin triggered by shifts in direct natural sunlight is a potential cause for Seasonal Affective Disorder (SAD), a common mood condition. However, while there is strong potential for this assertion to be correct, not enough official research studies have been performed to concretely establish the connection.

Melatonin Production

• Melatonin is produced by the pineal gland, which is a small area located at the top of the medulla oblongata in the brain. To produce melatonin, the pineal gland processes tryptophan, an amino acid that is known in popular culture as the abundant element in turkey meat that causes drowsiness after consumption. A major cue for pineal gland to increase the production of melatonin is darkness, and production is stymied by bright light. Therefore, the brain naturally has higher levels of melatonin during the dusk and nighttime hours than during the day.

Melatonin Effects

• While the exact purpose of melatonin in the human brain is not known, the effects of the hormone have been well documented by the medical community. In many circles it is jokingly referred to as the "hibernation" hormone because larger amounts of it cause drowsiness, a desire to eat foods rich in simple and complex sugars, and a desire to sleep for longer periods. Because of these properties, melatonin stimulation has been used to help individuals with sleep related medical or psychological disorders, such as chronic insomnia, bipolar disorder, and even jet lag.

SAD

• SAD is a depressive condition that manifests itself during the changing of the seasons from summer to fall or winter to spring. It is believed that the onset of symptoms, which include sadness, loss of energy, oversleeping and increased anxiety, is related to the shift in directness and intensity of sunlight that occurs with the change of the season. While there are two forms of SAD, winter and summer, winter is the most common. Anti-depressants and full spectrum light therapy help individuals manage and treat their symptoms.

Potential Links

• It is logical that melatonin has been suggested as a cause of SAD since the condition onsets during the darker months when there is less bright sunlight. Also, the depressive symptoms associated with SAD, such as lowered energy, increased desire to sleep and craving of sugars, match the symptoms of increased melatonin production. Similarly, the success of anti-depressants, which among other functions inhibits melatonin receptors, further encourages the hypothesis. However, the condition of summer SAD, which occurs when the natural sunlight is brightest, throws a wrench in the theory and has yet to be suitably confronted.

Study Results

• Over the past 10 years, there have been a few small studies performed to explore the link between melatonin and SAD, the most notable by Dr. Alfred J. Lewy. He has performed several studies since the late 1980s that compare the levels of melatonin in a control group and a group suffering from SAD to substantiate the link. Results have suggested that melatonin may affect a specific subgroup of SAD patients, though what their defining characteristics are have not been adequately identified.