Here we go:
Cannabis,[7] psychedelics, dissociatives, antidepressants, caffeine, nitrous oxide, and nicotine can all produce feelings resembling derealization, particularly when taken in excess. It can also result from alcohol withdrawal or benzodiazepine withdrawal.[8]
Derealization can also be a symptom of severe sleep disorders, and mental disorders like depersonalization disorder, borderline personality disorder, bipolar disorder, schizophrenia, and anxiety disorders.[9]
Interoceptive exposure can be used as a means to induce derealization, as well as the related phenomenon depersonalization.[10]"

I'm bipolar, coming off meds, drinking alcohol and smoking cigarettes. It's a really bad combo, but I guess as long as I am aware of it then I don't think it should cause a manic/depressive episode.

Brokencloud: The only other time it happens is when I am sitting down with my family eating dinner, but it's not as severe when I'm eating dinner. I'll have to tell myself "why, yes, this is real life. Why do I think otherwise?"

This hasn't happened before medication, but I've been on meds for over a year and this has just starting to happen since January. January was when I had made a big med reduction.