I have a brother-in-law who lives in the Pacific Northwest. He had issues with SAD. He dealt with it by replacing all his household lamps with 6500K LEDs. He says it works - for him (so this is anecdata).

One interesting (to me!) new-ish science thing I've run into is that we don't just have rods and cones in our retinas to detect light. The ganglia connecting all those together (and performing edge and possible shape detection) are also sensitive to bluish light and are connected with the autonomic systems (iris contraction, melatonin, etc.). This says some interesting things evolutionarily.