Think about Iceland, where it's cold and dark for a good part of the year. That country is the one with the lowest incident of depression, in the entire world.
And the reason is their diet.
Fish, fish, and more fish. ( even petrified shark ).
They also have the highest tissue levels of Omega-3 of any people in the world.
Omega -3 not only relieves depression, it prevents it as well.
When I visitied, I never had a bite of fish. I ate lamb every meal.
My favorite fish? Salmon.