Sunlight and nature - the two things most often cited as being good for the mind and body alike.
It makes me wonder if innately this is why retired people suddenly have the urge to spend months on a cruise ship, and why Florida is home to Canada's "snow birds."
I wonder how this applies to Phoenix. UV >= 12. I don't get sunburns though. Always sunscreen. I wonder if that's enough, and if I still get the benefit.