Delirium: First, Rule it OutPage 7 of 10

5. Differential Diagnosis for Delirium

I’m not insane; my mother had me tested.

Sheldon Cooper, “The Griffin Equivalency”
The Big Bang Theory (2008)

Delirium vs. Dementia

Delirium can be difficult to differentiate from other conditions like dementia or depression because many of the symptoms are similar. Those suffering with delirium can also have dementia at the same time, further hampering an accurate diagnosis (American Delirium Society, 2013; Rosenstein, 2011). Let’s look more closely at the differences, and similarities, between delirium and dementia.

The hallmark difference between delirium and other conditions is its rapid onset, its fluctuating course, and the patient’s inability to hold attention. Causes are usually reversible and often involve an underlying medical condition. Dementia, however, is a slowly progressive disease causing brain damage that can take years to develop.

In delirium, the level of consciousness can fluctuate, whereas it is steady in dementia.

Delirious patients have impaired orientation and are acutely confused; in those with mild dementia, orientation might be normal but will slowly progress to disorientation. Thinking, attention abilities, and awareness is often disorganized in delirious patients, while the attention capabilities of patients with dementia are usually intact and patients may even be alert during the day. Sleep/wake cycles are disturbed in those experiencing delirium, but patients with dementia may begin with normal cycles that slowly degrade as the disease progresses (Maneeton & Maneeton, 2013; NIH, Medline Plus, 2014a; Robertson, 2015 [pending]).

Delirium vs. Depression

Dying is just one thing to be sad about. Living unhappily, that’s another matter.

Morrie Schwartz
Tuesdays with Morrie (1992)

Depression, like delirium, can have a rapid onset, or it can be slow. While delirium has a myriad of possible causes, most are physiologic. The causes of depression are often a combination of factors including the environment (eg, stress, loss of a loved one, social isolation), genetics, biology (ie, neuro­transmitters), and psychological issues. Depression can last for months and can become chronic, although, like delirium, it can be resolved. As with delirium, a depressed person’s sleeping patterns can be disrupted, experiencing everything from insomnia to excessive sleeping. Two important distinctions in depression are the loss of interest in previously enjoyed activities and a pessimistic attitude (Maneeton & Maneeton, 2013; National Institute of Mental Health, 2011).

Source: Adapted from Eliopoulos, 2010.

Comparing Delirium, Depression, and Dementia






Rapid, hours to days

Rapid or slow

Progressive, develops overs several years


Medications, infection, dehydration, metabolic changes, fecal impaction, urinary retention, hypo- and hyperglycemia

Alteration in neuro­transmitter function

Progressive brain damage


Usually less than one month but can last up to a year

Months, can be chronic

Years to decades


Reversible, cause can usually be identified

Usually recover within months; can be relapsing

Not reversible, ultimately fatal

Level of consciousness

Usually changed, can be agitated, normal, or dull, hypo or hyperactive

Normal or slowed



Impaired short-term memory, acutely confused

Usually intact

Correct in mild cases; first loses orientation to time, then place and person


Disorganized, incoherent, rambling

Distorted, pessimistic

Impaired, impoverished


Usually disturbed, hard to direct or sustain

Difficulty concentrating

Usually intact


Can be reduced, tends to fluctuate


Alert during the day; may be hyperalert


Usually disrupted

Hyper or hypo somnolence

Normal for age; cycle disrupted as the disease progresses