Attention guys: What would cause a 180 degree personality change?

I'm extremely concerned about a friend of mine who recently told me he thought we shouldn't talk anymore. We used to be very close and would talk about anything. Although, he's never been one to get too deep into feelings and emotional stuff. It just strikes me as odd that one day he seemed genuinely concerned about things and like a week later; calls the whole friendship off. I know that guys sometimes need to go into 'cave mode' to sort stuff out, but how long does that usually last? does it depend on how much is going on? what kinds of things would cause some of you to blow someone off like that? I've got my own theories, but just looking for some other thoughts too.Attention guys: What would cause a 180 degree personality change?
does he have some new friends or a gf? they might have told him he couldnt talk to u anymore and he listenedAttention guys: What would cause a 180 degree personality change?
has he started seeing someone recently?

Has he started to hang out with a different group of people?

if the answer to the first question is yes, then it's because she told him to lose you.

if the answer to the second question is yes, then it could be drugs.

You know him so if you have your own theories then you probably already know the truth.