Delirium is defined as a disturbance of consciousness that develops rapidly over a short period of time and is reversible with treatment. Common clinical findings are rapid or rambling speech, impaired judgement and memory, and a fluctuating attention span and emotional state. Dementia differs in that onset occurs slowly and it is usually not reversible. Level of consciousness is intact, thought memory and judgement may become impaired. Delusional simply refers to a person experiencing a symptom of a mental disorder; delusions are beliefs or ideas that are contraindicated by reality and logic. Sundowning describes an increase in inappropriate speech or activity at night.