Only the far north of Norway has a long polar night, down south the days are short but not much different to many other places. In the north, the winter causes more sleep problems and some low mood/energy. (sources below)

But this is false equivalence as it's studying a different thing. Also it is very difficult to compare mental health studies across countries and attribute differences to single causes as there are so many confounding factors. In Norway there is a good standard of living, a social safety net, cheap healthcare and many other factors that are proven to be beneficial to mental health.

Humans are adaptable but sometime I think it's more accurate to say that humans tolerate different environments. We often don't adapt to them, we cope with them.

[1] https://www.cambridge.org/core/journals/psychological-medici... [2] https://bmcpsychiatry.biomedcentral.com/articles/10.1186/147...