Schizophrenia and delusional disorder are distinct disorders that may share certain features, such as paranoia, suspiciousness, and unrealistic thinking. However, schizophrenia is associated with psychosis—a loss of contact with reality—and with a decline in general functioning. In contrast, in delusional disorder, contact with reality is preserved except for the very specific and focused unrealistic thinking in the delusions, and functioning is much less impaired. In addition, schizophrenia is relatively common, whereas delusional disorder is rare.
Last full review/revision June 2008 by Juan R. Bustillo, MD