**4. Conclusion**

Delirium is a common condition, especially in the elderly and in patients with severe illness. Delirium is associated with longer hospital stay, poorer functional outcome, and cognitive decline. Also, it is associated with elevated morbidity and mortality. Understanding etiology of delirium is important because treatment of delirium is identification and reversal of etiological factors. Etiological factors are of two types: predisposing and precipitating factors. The risk of delirium should be kept in mind when approaching to a patient with predisposing factors like increased age, cognitive impairment, hip fracture on admission and severe illness are among the most common ones. The presence of precipitating factors (the acute insults that trigger the mechanisms resulting in delirium) like anemia, hypoxaemia, electrolyte abnormalities, sleep deprivation, pain, bladder catheter use and drugs should be evaluated and be treated promptly if possible.
