Delirium is a neuropsychiatric syndrome defined by acute onset, fluctuating course and disturbances of consciousness, attention, orientation, memory, thought, perception and behaviour. In this book, the authors present topical research in the study of delirium, including the risk factors for developing postoperative delirium in surgical intensive care unit patients; the prevalence, epidemiology and risk factors of delirium in elderly medical inpatients; the relationship between brain disease and neurotransmitter systems in the pathophysiology of delirium; white matter changes in delirium and the association of apolipoprotein E and delirium.