Just guessing here, but if you're depressed you're much less likely to take your health seriously. It's also much easier to abuse drug when you're lonely - look at drug use among the homeless.

Certainly, if I took away your friends and family I would expect your health to decline.

> Depression and anxiety cause elevated cortisol levels which cause all kinds of physically measurable issues.

I hadn't thought about it that way. I suppose elevated cortisal causes a kind of domino effect that ends up with deteriorated overall health.

> Just guessing here, but if you're depressed you're much less likely to take your health seriously. It's also much easier to abuse drug when you're lonely - look at drug use among the homeless.

> Certainly, if I took away your friends and family I would expect your health to decline.

This makes sense. I haven't been considering the general population because I consider myself a lonely person since I spend most of my time coding and reading books but that's now how most lonely people would be classified. Many are homeless and in much worse circumstances than I am. I shouldn't be using myself as an example for that reason.