The hormone ___________, secreted by the pineal gland, has been implicated in seasonal affective disorder.

A) lanin
B) progesterone
C) melatonin
D) serotonin
E) gaba

Melatonin is the hormone secreted by the pineal gland and has been linked to seasonal affective disorder (SAD). SAD is a type of depression that occurs during specific seasons, typically the winter months in areas with reduced sunlight. Melatonin production is stimulated by darkness and suppressed by light, and disruptions in the sleep-wake cycle due to changes in daylight exposure can lead to changes in melatonin production and subsequent mood alterations.