Delirium vs Dementia vs Depression
An 80-year-old is confused and withdrawn — is it delirium, dementia, or depression? Each demands a completely different response. Choosing wrong means missing a life-threatening infection in delirium, withholding antidepressants in depression, or futilely trying to "cure" dementia.
Side-by-side comparison
Side-by-side3 compared
Comparevs
Dimension
Delirium
Dementia
Depression
Onset & course
- ★Acute (hrs–days); fluctuates, worse at night
- Insidious (months–years); steady decline
- Variable (weeks–months); mood-driven
Signs & symptoms
- Clouded consciousness; impaired attention
- Visual hallucinations; reversed sleep-wake
- ★Recent memory lost first; remote preserved
- Consciousness clear until late
- ★'I don't know' answers; recalls with cues
- Apathy; early-morning waking
Reversibility / workup
- ★REVERSIBLE — find cause (UTI, meds, hypoxia)
- Irreversible, progressive
- Reversible; screen PHQ-9 / GDS
Priority care
- Correct underlying cause; reorient; avoid restraints
- Maintain routine; support ADLs; reduce stimuli
- Screen suicidality; promote socialization
Treatment & meds
- Treat cause; minimize sedatives
- Donepezil; memantine
- SSRIs, therapy; ECT for severe
Family / caregiver
- Often resolves with treatment; expect fluctuation
- Safety-proof home; caregiver respite
- Meds take weeks; watch for suicidality
Red flags — escalate
- Acute change = emergency; rule out hypoxia/sepsis
- Rapid decline → assess superimposed delirium
- ★Active suicidal ideation/plan
Complications
- Untreated → death, prolonged stay
- Total dependence; aspiration
- Suicide; functional decline
Onset & course
Delirium
- ★Acute (hrs–days); fluctuates, worse at night
Dementia
- Insidious (months–years); steady decline
Signs & symptoms
Delirium
- Clouded consciousness; impaired attention
- Visual hallucinations; reversed sleep-wake
Dementia
- ★Recent memory lost first; remote preserved
- Consciousness clear until late
Reversibility / workup
Delirium
- ★REVERSIBLE — find cause (UTI, meds, hypoxia)
Dementia
- Irreversible, progressive
Priority care
Delirium
- Correct underlying cause; reorient; avoid restraints
Dementia
- Maintain routine; support ADLs; reduce stimuli
Treatment & meds
Delirium
- Treat cause; minimize sedatives
Dementia
- Donepezil; memantine
Family / caregiver
Delirium
- Often resolves with treatment; expect fluctuation
Dementia
- Safety-proof home; caregiver respite
Red flags — escalate
Delirium
- Acute change = emergency; rule out hypoxia/sepsis
Dementia
- Rapid decline → assess superimposed delirium
Complications
Delirium
- Untreated → death, prolonged stay
Dementia
- Total dependence; aspiration
★ marks the fact that sets a column apart.
Clinical Pearl
Delirium is acute and reversible — treat it. Dementia is gradual and irreversible — manage it. Depression is treatable — screen for it.
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