Why does sunlight make people happy?

Increases serotonin: Serotonin is known as the chemical the brain produces and it stabilizes your mood. For many patients, i also recommend a light box and sometimes this is all that is needed for depression. Sunlight makes you happy too because you enjoy good weather.

Complex: Light does many things, it produces vitamen d which when low can cause depressive symptoms. It also supresses the production of melatonin which makes us sleepy and regulates are biologic clock. Some depression seems to be a loss of syncronization of our hormone levels and sleep wake cycles such that we feel asleep when we are awake.