Harvard: "Exercise is an all-natural treatment to fight depression"

https://www.health.harvard.edu/mind-and-mood/exercise-is-an-...

"Seasonal Affective Order, or SAD ... has been linked to vitamin D, otherwise known as the sunshine vitamin, because the skin absorbs it through exposure to sunlight."

https://www.va.gov/washington-dc-health-care/stories/combati...

"Consider adding some of these steps into your daily routine to improve your mood:"

"Spend time outside to get ample vitamin D ... Eat foods rich in vitamin D (salmon, eggs, tuna, etc.) Take vitamin D supplements"