I have to disagree. Having abused the hell out of Ketamine for 2 years straight (and used in moderation for years before that), at least during those last 2 years of abuse I started believing all kinds of crazy shit, had some schizophrenic breaks, just really really bad mental health caused by Ketamine.
Those kinds of subtle realizations are not the makings of psychosis. If by psychosis you are simply referring to feelings of grandeur, "I am Christ", and general ego inflation. Well, Ketamine made me think those things. Thoughts like that never crossed my mind on MXE.
That said, if MXE is causing you psychosis, you should probably discontinue use.