Introduction

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 that comprises the delusions; functioning is much less impaired. In addition, schizophrenia is relatively common, whereas delusional disorder is rare.