Merck Manual

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What Is Confusion?

What Is Confusion?

Confusion means different things to different people, but doctors use the term to describe people who cannot process information normally.

Confused people cannot

  • Follow a conversation

  • Answer questions appropriately

  • Understand where they are

  • Make critical judgments that affect safety

  • Remember important facts

Confusion has many different causes, including the use of certain drugs (prescription, over-the-counter, and illegal) and a wide variety of disorders. Delirium and dementia, though very different disorders, both cause confusion.

When a person is confused, doctors try to determine what the cause is, particularly whether it is delirium or dementia.

If confusion develops or worsens suddenly, the cause may be delirium. In such cases, medical attention is needed immediately because delirium may be caused by a serious disorder. Also, treating the cause, once identified, can often reverse the delirium.

If confusion develops slowly, the cause may be dementia. Medical attention is needed but not urgently. Treatment may slow the mental decline in people with dementia but usually cannot stop the decline.