SAD and cancer rates go up somewhat with latitude, definitely by 35-40N. But it is complicated because it doesn't affect everyone the same way. e.g., most of Eu

SAD and cancer rates go up somewhat with latitude, definitely by 35-40N. But it is complicated because it doesn't affect everyone the same way. e.g., most of Europe is living above 40N. In some cases, availability of natural light (due to tree cover, weather, and position in timezone) is as important as latitude. I would guess that some people are simply better at living at more extreme latitudes or with a weaker circadian signal. Several researchers have tried to use particular genetic markers to explain this, but I don't know a specific one that explains all of it.