I don't think mental illness makes one think too much and I don't think it's the sole reason for isolation. I think there are multiple factors that can lead to it, and as you get older its normal to lose friends. I only say this because I look at my parents and they have a few good friends but not a lot...and almost none of their friends are from their adolescent years.

I can understand how it can be painful though. But then you have to also remember if you're camera shy or not. I know I am pretty camera shy and I don't have a lot of pictures of myself despite having a good number of friends. I see them post pictures of themselves, and mutual friends, but not of me. It doesn't really bother me. I admit, though, that it is hard to keep in contact with people. Of all my friends in high school I may occasionally talk to about 5 and I graduated 4 years ago. It's hard to keep up with people when you don't see them on a daily basis.

Also my boyfriend has been out of high school for 5 years, and I believe he only talks to 2 people still. (1 he talks to like once a year)