Depression, Delirium and Dementia

It is important to understand the difference between depression, delirium, and dementia and a person with dementia could be admitted to hospital with all three conditions.  Cognitive impairment that mimics dementia may be associated with delirium or depression. These conditions usually respond to treatment of the underlying cause.  Conditions that need to be differentiated from dementia include:

  • Normal memory changes of ageing
  • Delirium
  • Depression
  • Side effects of drugs
  • Thyroid disorders
  • Infections
  • Vitamin deficiency
  • Brain tumour


Is a mood disorder and has a major impact on people’s functioning and quality of life.  It can be an early sign of dementia and a person can also feel anxious, experience hallucinations or periods of agitation.   Mild depression can be treated with a psychological treatment called ‘talking therapies’ and other interventions, but medication may be considered in more severe clinical depression.  Depression can have a gradual onset and people may have difficulty concentrating, be easily distracted, and have intrusive negative thoughts.  They may have feelings of helplessness and low self-esteem. Depression in older people with dementia is common and is easily overlooked or mistaken as part of the process of dementia.  However it is possible to Live Well with Dementia and so any symptoms of depression must be taken very seriously and reported to the GP.


May be the only sign of a serious complication in an older person and so it is essential to identify delirium and treat the underlying cause.  Delirium is typified by a rapid change of cognition and is characterised by hallucinations, clouding of consciousness and misinterpretation of events, as well as sleep disturbance.  Delirium may last for 30 days or more and is associated with some underlying physiological condition like injury, disease, chest or urinary infections, Constipation, poisons, alcohol, medications or dehydration.   It can occur in up to 50 per cent of patients aged 65 years and over who have been admitted to hospital, and higher rates are seen among surgical patients and in intensive care.  Dementia is a significant risk factor for the development of delirium.  Being able to differentiate between dementia and delirium is essential for staff in acute care settings.  Any change in environment can also contribute to the onset of delirium for older people and people with dementia through:

  • Environmental changes
  • Increased or decreased sensory stimuli
  • Sleep deprivation
  • The stress of being in a foreign and often frightening new environment.
  • Hearing or visual deficit also places the patient at risk of developing delirium

(Hanley, 2004)

The sooner delirium is detected the better the outcome.  It is a medical emergency.  Further information on the characteristics of Depression, Delirium and Dementia.