I don't know the answer to this. I know, in my case, I seem to have quite a bad case of nerves. But I don't have anything to be anxious about. What I've concluded is that, after a lifetime of running on my nerves & struggling with anxiety over one thing after another, my body simply no longer knows how to be any other way. I do also think age plays a role as well. I think as people age they often have more difficulty with nerves in general. Perhaps the difference is that anxiety is a reaction to something such as an upcoming potentially difficult event or situation (either real or perceived) while "nerves" simply exist independent of anything in particular that's going on? At least that's my thinking with regard to your post.