Sunlight Makes Skin Produce Serotonin

Aside from vitamin D, human skin also makes serotonin directly when it is exposed to sunlight. Researchers studying skin photobiology have shown that ultraviolet radiation activates biochemical pathways in the skin that produce serotonin, a key neurotransmitter involved in mood and circadian rhythms. This local serotonin production helps explain why sunlight can influence mood and bodily rhythms even before any signals reach the brain.

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