I don't know if this counts as either derealization or depersonalization. But I have episodes where I feel like my consciousness is withdrawing, imploding, or perhaps collapsing in on itself... becoming hyper-focused on my own consciousness to the exclusion of everything and everyone else around me. It's sort-of like experiencing a mental black hole where my consciousness is being pulled down into itself while whatever, or whoever, happens to be around me sort-of forms an event horizon... it's there... but at a "safe" distance, if that makes any sense. It's an odd experience.

I haven't had much of this recently, at least not at as intense a level as it sometimes has been. But it was only a few months ago when it was occurring pretty-much daily. And, when it does occur, it tends to be around the dinner hour. So I began to think of it as, perhaps, a type of what is sometimes referred to as Sundown Syndrome. Actually though, as I think back, I can recall 1 or 2 times, decades ago when I was in college, when I had this type of experience as well. So I presume it has / had something to do with anxiety. Nowadays, when it does occur, I don't really do anything in particular to address it. Since it's an experience I'm familiar with I simply let it be and wait for it to subside, which it does.