I'm an extreme introvert, some would say loner (I don't like the negative connotation). I felt pressure to not be this way when I was younger but I am very comfortable with it now. In my job I am either talking to people face to face or on the phone all the time. I enjoy a lot of solitude when I'm not at work.
It didn't cause my alcoholism but it may have made all the socializing I was making myself do in those days easier.