I agree that the lack of sunlight can have a powerful effect on us. This is bourne out through the studies on suicide rates.

The further north we are on the planet the higher the incidence of suicide so it isn't much of a jump to think that it has other major health impacts.

Country Population Total Number Per Year Crude Suicide Rate Rank
Lithuania 2,864,459 913 31.9 suicides per 100k 1
Russia 143,895,551 44,607 31 suicides per 100k 2
Guyana 786,508 229 29.2 suicides per 100k 3
S.Korea 51,339,238 13,810 26.9 suicides per 100k 4
Belarus 9,433,874 2,471 26.2 suicides per 100k 5
Suriname 573,085 130 22.8 suicides per 100k 6
Kazakhstan 18,592,970 4,183 22.5 suicides per 100k 7
Ukraine 43,795,220 9,810 22.4 suicides per 100k 8
Latvia 1,911,108 405 21.2 suicides per 100k 10
Lesotho 2,292,682 486 21.2 suicides per 100k 9
Belgium 11,562,784 2,393 20.7 suicides per 100k 11
Hungary 9,655,361 1,844 19.1 suicides per 100k 12

Source

Anything that gets people up and out is a good idea. There is a tendency in northern climes to spend a lot of time indoors.

The allergies definitely feel much more prevalent these days. Someone having a peanut allegy was very rare and novel idea not so long ago?

Guyana seems like an interesting place?