[TheSpiceIsLife]

I think I might have heard this at some point in the past.

Anyway, I found a reference to support your claim:

Also consistent with the conclusions of Torrey1 and Saha et al,2 our analyses shown in table 3 found a strong tendency for prevalence to increase with latitude.[1]

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2669590/

[intralizee]

I'm not aware from the article of how the illness "schizophrenia" foreshadows all of mental health. My illness being Gender Dysphoria.

Vitamin D deficiency from what I've read is common everywhere. It does make sense that longer winters would impact a person such as staying inside more. Yet I doubt any evidence can confirm lack of Vitamin D is associated with the illness schizophrenia.

[TheSpiceIsLife]

Ah, yeah, that's a good point. Schizophrenia is probably a poor proxy for all mental illness.

And there's probably at least quite a few things that aren't mental illness that benefit from mental healthcare.