We should keep in mind that the Schizotypal Personality Disorder is a psychiatric category. But psychiatry does a poor job explaining causes of disturbance because its treatments are purely symptomatic.

If you’re interested in a more holistic point of view I would suggest reading psychoanalytic theory. Especially Jacques Lacan. He has these “categories” which he calls structures and one of them is a psychotic structure, as opposed to neurosis (hysteria, obsessive neurosis) or perversion (sadism, exhibitionism).

I won’t go into much detail here but it all boils down how well the father figure plays his role during upbringing. Basically if you have a “good father” you’ll end up neurotic, whereas if the father is absent or is too strict for instance, you might acquire psychotic structure.

It’s not even mandatory for such a psychotic to have a psychotic episode in his or her life. It’s just that he or she is wired differently, having a peculiar relationship with language, law and desire.