There is such a thing as "delusional guilt," often seen in severe depression with psychotic features. But the guilt has not caused psychosis. Psychosis can have many underlying medical etiologies (etoh withdrawl, cocaine binges, electrolyte imbalances, dementia, schizophrenia, just to name a few) and guilt is not one of them. However, extreme stress can lead to a psychotic break in people with schizophrenia or in those who have had psychotic episodes in the past.
Are you gonna tell me it all because of my refrigerator mother, Mr.Freud? 🙂