In an article titled "Hypnosis: Its Renascence as a Treatment Modality" (p. 52 of Collected Papers, Vol. 4 by Erickson and Rossi (Irvington Pubs, 1980), you can read some of Dr. Erickson's thoughts about treatment of psychosis.
In (very) brief, we might say that Erickson would make use of the communication offered by the client (utilization) and then help the client retrieve and organize the experiential learnings they required to function more effectively at the particual stage of their life. Whether the communication was as highly discounted as that provided by a "psychotic" or not was irrelevant except for the extra effort required by the therapist to use it in a responsible fasion. I hope that helps point to some research material and gives you a bit of a handle on it.