This document defines and describes delusional disorder. It is characterized by non-bizarre delusions that have persisted for at least one month without significant impairment in functioning. There are several proposed causes including biological and psychosocial factors. Various subtypes are identified based on the predominant delusional theme, such as erotomanic, grandiose, jealous, persecutory, and somatic delusions. The diagnostic criteria require non-bizarre delusions for at least one month without symptoms meeting criteria for schizophrenia.