|What's unsaid here is that the dream content does not differ between the schizophrenics and normal controls. As Freud noted, we are all psychotic when we dream. The only difference is how the dreamer talks about the dreams, with the schizophrenic dream accounts reflecting their poverty of speech (a negative symptom of schizophrenia).
Real Clear Science
"[A] team of Brazilian researchers has demonstrated that the word patterns a person uses when describing a dream can distinguish between schizophrenia and bipolar disorder, a pair of mental illnesses that are often difficult to tell apart.
The authors interviewed 60 people who were either healthy, schizophrenic or bipolar. They were asked to recount a previous dream. Their responses were transcribed and changed into word graphs. (See panel A in the figure below. Each dot represents a word, and dots were connected based on when the person spoke them.)
As shown in panel B, schizophrenic and bipolar patients displayed strikingly different word graphs from each other and from healthy controls. Schizophrenics tend to discuss their dreams using very few words, while those with bipolar tend to speak excessively and repetitively.
Interestingly, creating word graphs from stories told by the volunteers about a time when they were awake yielded far less useful results. There is something about describing a dream in which the underlying pathologies become much more obvious.
Thus, the authors conclude, "The Freudian notion that 'dreams are the royal road to the unconscious' is clinically useful, after all."Source: Natália B. Mota et al. "Graph analysis of dream reports is especially informative about psychosis." Scientific Reports 4, Article number: 3691. Published: 15-January-2014. doi:10.1038/srep03691