[Question] Sunscreen. When? Why? Why not?

Hello,

I’ve been won­der­ing about sun­screen’s effec­tive­ness in re­duc­ing can­cer risk.

The gen­eral im­pres­sion I’ve got­ten in my (ad­mit­tedly brief) re­search on it seems: “If you know you’ll be ex­posed for a long du­ra­tion in the sum­mer/​spring, then yes, wear sun­screen. Other­wise, Vi­tamin D gen­er­a­tion takes pri­or­ity.” (re­lated)

I’ve looked around on less­wrong, and can’t find any re­ally all-en­com­pass­ing in­for­ma­tive posts about it. The most in­ter­est­ing com­ment I’ve seen was by Tem42, who refer­ences a study that claims that over­all can­cer rates are ac­tu­ally lower in south­ern states vs north­ern states.

Is my gen­eral im­pres­sion cor­rect enough? Or should peo­ple be lath­er­ing sun­screen all the time; or not at all?

Thanks in ad­vance!