96 Schizophrenia Spectrum and Other Psychotic Disorders
Differential Diagnosis
Other medical conditions. A variety of medical disorders can manifest with psychotic
symptoms of short duration. Psychotic disorder  due to another medica l condition or a de-
lirium is diagnosed when there is evidence from  the history, physical examination, or lab-
oratory tests that the delusions or hallucinati ons are the direct physiological consequence
of a specific medical condition (e.g., Cushing’s syndrome, brain tumor) (see “Psychotic
Disorder Due to Another Medical Co ndition” later in this chapter). 
Substance-related disorders. Substance/medication-induced psychotic disorder, sub-
stance-induced delirium, and substance intoxication are distinguished from brief psychotic
disorder by the fact that a substance (e.g., a drug of abuse, a medication, exposure to a toxin)
is judged to be etiologically related to the psychotic symp toms (see “Substance/Medication-
Induced Psychotic Disorder” later in this chapte r). Laboratory tests, such as a urine drug
screen or a blood alcohol level, may be helpful in making this determination, as may a care-
ful history of substance use with attention to  temporal relationships between substance in-
take and onset of the symp toms and to the nature of the substance being used.
Depressive and bipolar disorders. The diagnosis of brief psychotic disorder cannot be
made if the psychotic symptoms are better explained by a mood episode (i.e., the psychotic
symptoms occur exclusively during a full major depressive, manic, or mixed episode). 
Other psychotic disorders. If the psychotic symptoms pers ist for 1 month or longer, the
diagnosis is either schizophr eniform disorder, delusional disorder, depressive disorder
with psychotic features, bipolar disorder with psychotic fe atures, or other specified or un-