INTRODUCTION
Delusional disorder is characterized in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) as the presence of one or more delusions for a month or longer in a person who, except for the delusions and their behavioral ramifications, does not appear odd and is not functionally impaired [1]. Prominent hallucinations and other psychotic or marked mood symptoms are absent. Nonprominent hallucinations and odd behaviors related to the delusional theme may be present.Delusional disorder is not well studied relative to other psychotic disorders, such as schizophrenia. Much of the information in the sections on epidemiology, course, and treatment is drawn from small samples or based on clinical experience. Longitudinal and population-based studies are needed to better characterize the disorder and clinical trials are needed to identify effective treatments.
This topic discusses the epidemiology, pathogenesis, clinical manifestations, course, diagnosis, and treatment of delusional disorder. Clinical manifestations, differential diagnosis, and initial management of psychoses are discussed separately. The epidemiology, pathogenesis, clinical manifestations, course, diagnosis, and treatment of delusional parasitosis, a delusional disorder of the somatic type, are also described separately. (See "Psychosis in adults: Epidemiology, clinical manifestations, and diagnostic evaluation" and "Delusional infestation: Epidemiology, clinical presentation, assessment, and diagnosis" and "Treatment of delusional infestation".)
EPIDEMIOLOGY
Prevalence — The lifetime morbid risk of delusional disorder in the general population has been estimated to range from 0.05 to 0.1 percent [2-4], based on data from various sources including case registries, case series, and population-based samples. The epidemiology of delusional disorders has not been studied in large, community-based samples. These findings and the DSM-5 estimated lifetime prevalence of delusional disorder (0.2 percent) [1] are far lower than the estimated lifetime prevalence for other major psychotic disorders, such as schizophrenia (0.3 to 0.87 percent) and bipolar I disorder (0.24 to 0.6) [5]. Rates of delusional disorder reported in samples of patients receiving mental health treatment have ranged from 0.5 to 1.2 percent [2,6,7].
Attempts to quantify incidence estimates (0.7 to 3.0 out of 100,000) have been based on hospital admission data of uncertain accuracy [2].