Sufis can be placed under different categories.
Only some of them are schizophrenics.
Many of them are frank forgers. They pretend to receive knowledge directly from God. Instead of WAHI (Divine Revelation) they call their "experience" KASHF or ILHAM.
Others sincerely believe that through KASHF and ILHAM (spiritual trance) they communicate with God and God communicates with them. They are, in fact, claiming prophethood since after Muhammad (S) the door to Divine Revelation has been closed forever. The intense ascetic life style, self-denial or self-effacement with excessive worship and RIYADHAT (extreme rites and rituals, self-infliction, sleeplessness) have hurt them and affected their mind adversely. They are subject to all kinds of hallucinations and delusions.