Along with the question of some early defense, another important variable is the deutero stage (combined parent imago). This decrease in the power of the superego (i.e. the low ego ideal) means that it the measurement of oneself at a given stage is undermined. This may make it easier for a regression from higher stages. It may even be part of the early stage scotomization.
Another important factor in psychosis concerns the particular ego injury of a humiliation/betrayal in both one's work life and love life at the same time. (To this is might be possible to add a problem with friends as well.) In my clinical experience there have been at least three patients who had a psychotic break after they were working with a boss that criticized them and went out of his way to either put them in a dangerous situation, have them fired, or demoted. At the same time there was either a break up with a girlfriend or a betrayal in her cheating.
The patients themselves strongly registered the fact that both things happened at the same time. One of them emphasized that it was when the girlfriend began working for the boss and the idea of him "talking shit" to her was a possibility, that the situation became really painful.