Acute confusional state which is also known as ACS refers to a psychiatric Condition of severe confusion or rapid change in brain function. This often occurs as the result of a mental illness or physical illness.

Acute confusional state symptoms include lethargy, agitation, confusion, disorientation and delirium.

Acute confusional state is also known as delirium based on DSM-III-R. (See ACS, Delirium)