Hormone melatonin in seasonal affective disorder (SAD)

Seasonal affective disorder or SAD is a type of recurring major depression with a seasonal pattern. The exact cause of SAD is not fully understood, but it is thought to be linked to reduced exposure to sunlight during the shorter days of the year.

Seasonal affective disorder is commonly known as seasonal depression or the “winter blues.” It is a subtype of major depression that occurs due to changes in climate and seasonal weather. Sunlight plays a critical role in the decreased serotonin activity, increased melatonin production, disrupted circadian rhythms, and low levels of Vitamin D associated with symptoms of SAD.

People with SAD may also have difficulty with overproduction of melatonin. Melatonin is a hormone produced by the pineal gland that responds to darkness by causing sleepiness. Melatonin promotes calmness and relaxation, helping individuals rest their bodies and minds in order to fall asleep

Melatonin is a hormone produced in the pineal gland in the brain. Its production is controlled by body’s master clock, found in the suprachiasmatic nucleus.

During the day, hormone melatonin levels are low. But as it gets dark, optic nerves send signals to the master clock, which signals the brain to begin producing melatonin.

People who suffer from SAD may overproduce melatonin, causing them to feel sleepy and lethargic during the day. This is common for people who experience SAD in the winter.
Hormone melatonin in seasonal affective disorder (SAD)

Melatonin and seasonal affective disorder

In human, as in other mammals, melatonin is primarily a hormonal signal of darkness. One of the major interests in melatonin in the central nervous system is with regard to the possible mechanism of mood variations in response to light.

This phenomenon has been under intensive study in recent years and has been defined as syndrome called seasonal affective disorder.

In seasonal affective disorder recurrent episodes of depression occur during winter months and euthymia during summer season. These patients have delayed circadian rhythms.

In people with seasonal affective disorder, the photoperiodic hypothesis proposes that the period of melatonin release at night is longer in the winter than it is in the summer, whereas in people with seasonal affective disorder, how long the body is releasing melatonin each night does not differ across the season.
Melatonin and seasonal affective disorder