Paprika

This trailer for the japanese animated movie Paprika looks interesting. The plot seems to be reminiscent of that of Roger Zelazny's The Dream Master.

Was Zelazny's novel the first to feature a psychologist entering his patient's dreams? That premise is shared by a few novels published afterwards (like Greg Bear's Queen of Angels). But I can't recall any example older than The Dream Master. The closest thing I can think of is the solipsistic nightmare towards the end of Bester's The Demolished Man, and when the protagonists of Philip K. Dick's Eye in the Sky enter each other's concretely manifested personal worldviews.