There can be quite a few different causes behind hallucinations. Could be something neurological or could be mental illness. Schizophrenia (I'm not a doctor but I don't think that's what is going on here), bipolar disorder, major depressive disorder and -- in my case -- PTSD are all examples of mental illnesses that can cause hallucinations. Sometimes stress in itself can cause these symptoms. In my case, I'm told that my issues stem from trauma and major depression (major depression tends to amplify things). My hallucinations can be easily linked to a past trauma or have absolutely nothing to do with my trauma and seem completely random. Last night was hard for me with hallucinations,