Is there a particular illness or disorder that would cause one to believe they don’t exist? I know I exist, but especially when things are going bad, and sometimes just seemingly randomly, the sentence “I do not exist” pops up into my head and just kinda, repeats itself until I stop it. I stop it by reaffirming to myself that I do exist. Sometimes if I’m wrapped up in it enough it’ll be out loud, semi-consciously. I’ve never had any trouble believing the world exists, or other people exist, but I just kinda wonder about why my brain is like that when it comes to me. It’s an instinctual thing so far in my life, not something I ever have actually believed