What is Seasonal affective disorder?

Seasonal affective disorder (SAD) is a type of depression that comes and goes as seasons change. The most prevalent form of SAD arrives in the fall and winter and lifts during the spring and summer.

Most scientists believe that the primary cause of SAD is diminished sunlight that accompanies the shorter days in the winter.

For many people, reduced light triggers changes that reverberate throughout their bodies and minds causing their moods to darken.

It has been hypothesized that the circadian hormone melatonin is involved in SAD. Melatonin is a hormone that aids the body in sleeping.

Melatonin is a ‘night’ signal released from the pineal gland, which activates M1 and M2 receptors found in the brain clock, the suprachiasmatic nucleus (SCN), and which modulates the circadian rhythm generated by the clock.

Light inhibits the activity of hydroxytryptamine-o-methyltranferase, which coverts serotonin to melatonin. Without adequate sunlight, serotonin may be lost by being converted to melatonin.
What is Seasonal affective disorder?