Alternative diagnosis	Distinguishing features
Brief psychotic disorder	Presence of delusions, hallucinations, disorganized speech, or grossly disorganized or catatonic behavior lasting at least one day but less than one month
Delirium	Multiple underlying etiologies; symptoms often similar to positive symptoms of schizophrenia but with a much shorter course
Delusional disorder	Delusions are not bizarre, and there are no other characteristics of schizophrenia
Medical illnesses	Illnesses that may cause schizophrenia-like symptoms include hepatic encephalopathy, hypoglycemia, electrolyte abnormalities (e.g., hyponatremia, hypercalcemia, hypocalcemia, hypomagnesemia), and sepsis; symptoms resolve with treatment of underlying condition
Medication-induced disorder	Medications that may cause schizophrenia-like symptoms include anticholinergics, anxiolytics, digoxin, phenytoin (Dilantin), steroids, narcotics, and cimetidine (Tagamet); symptoms resolve with discontinuation of medication
Mood disorders with psychotic features	No major depressive, manic, or mixed episodes have occurred concurrently with active phase symptoms; or, if they have occurred, their total duration has been brief relative to the duration of the active and residual symptoms
Pervasive developmental disorder	Recognized during infancy or early childhood; absence of delusions and hallucinations
Psychotic disorder NOS	This diagnosis is made if there is insufficient information available to choose between schizophrenia and other psychotic disorders
Schizophreniform disorder	Lasts one to six months; diagnosis does not require a decline in functioning
Schizotypal personality disorder	Pervasive patterns of social and interpersonal deficits beginning in early adulthood; accompanied by eccentric behavior and cognitive or perceptual distortions
Substance abuse	Multiple substances (e.g., hallucinogens, narcotics, alcohol) and withdrawal from these substances can cause delusions and hallucinations