I vote starvation. I think a big percent of the world will starve, with a few countries holding out. A bit later I think all those people will starve too, with only like 20 billionaires surviving. And then when THEY run out of food a few years later, I dunno, they'll OD on drugs?
I can't image HR getting a complaint that you aren't making small talk, and saying "That's outrageous! We'll demand his medical records right now!"
HR exists to keep the company from getting sued, and I think there's a lot less risk for them to tell one employee "He doesn't want to talk to you, deal with it." vs demanding medical records for a non-work-role related issue.