High rates of delirium and depression are reported in people with dementia so these conditions may co-exist and each needs to be addressed. Dementia and depression are also risk factors for delirium.
Depression, dementia and delirium have some features in common. Depression and delirium, particularly hypoactive delirium, may present with apathy, withdrawal and tearfulness. Delirium occurs suddenly (over a matter of hours or days) and the symptoms tend to fluctuate throughout the day; depression describes a negative change in mood that has persisted for at least two weeks; and the onset of dementia is generally slow and insidious.
Differentiating depression from dementia and delirium requires knowing the characteristic features of each condition (see table below) and establishing the patient’s premorbid cognitive status and mood. This involves obtaining the patient’s history (from the patient or if cognitively impaired from an informant - family or carer or staff) and conducting a depression, cognitive and delirium screen.
| Feature | Dementia | Delirium | Depression |
|---|---|---|---|
| Onset and duration | Slow and insidious onset; deterioration is progressive over time. | Sudden onset – over hours or days; duration – hours to less than one month, but can be longer. | Recent change in mood persisting for at least two weeks – may coincide with life changes – can last for months or years. |
| Course | Symptoms are progressive over a long period of time; not reversible. | Short and fluctuating; often worse at night and on waking. Usually reversible with treatment of the underlying condition. | Typically worse in the morning. Usually reversible with treatment. |
| Psychomotor activity | Wandering/exit seeking Agitated Withdrawn (may be related to coexisting depression) | Hyperactive delirium: agitation, restlessness, hallucinations Hypoactive delirium: sleepy, slow-moving Mixed: alternating features of the above. | Usually withdrawn Apathy May include agitation |
| Alertness | Generally normal | Fluctuates, may be hyper-vigilant through to very lethargic. | Normal |
| Attention | Generally normal | Impaired or fluctuates, difficulty following conversation. | May appear impaired |
| Mood | Depression may be present in early dementia | Fluctuating emotions – for example: anger, tearful outbursts, fear | Depressed mood Lack of interest or pleasure in usual activities Change in appetite (increase or decrease) |
| Thinking | Difficulty with word-finding and abstraction | Disorganised, distorted, fragmented | Intact; themes of helplessness and hopelessness present |
| Perception | Misperceptions usually absent (can be present in Lewy body dementia) | Distorted – illusions, hallucinations, delusions; difficulty distinguishing between reality and misperceptions | Usually intact (hallucinations and delusions only present in severe cases) |
Delays in investigating and treating underlying reasons for cognitive impairment, or initiating inappropriate treatment, can have serious consequences for an older person’s health and wellbeing whilst they are in hospital and on discharge.
Delirium must be differentiated from Dementia with Lewy Bodies
It is important to differentiate delirium from Dementia with Lewy Bodies (DLB). These conditions can appear identical, however, haloperidol, which may sometimes be used to manage delirium symptoms, can cause severe movement disturbances (such as spasms or rigidity) and can even be fatal to some patients with DLB. The presence of parkinsonism helps in differentiating DLB from delirium.1
1. Gore, R.L., E.R. Vardy, and J.T. O'Brien, Delirium and dementia with Lewy bodies: distinct diagnoses or part of the same spectrum? J Newurol Neurosurg Psychiatry, 2014. 23.
Reviewed 17 July 2024