Widely known as the three Ds, dementia, delirium, and depression share similar symptoms yet are very different in nature. In this article, we shall explore the common denominators of these three conditions and learn how to manage them by understanding the distinctions between dementia, delirium, and depression.1 By knowing the similarities and differences, caregivers and persons who display symptoms will be able to better manage them and seek appropriate professional help.
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Dementia, Delirium, and Depression at a Glance
- Dementia is an umbrella term that describes a wide range of symptoms that includes changes in behaviour, difficulty in planning, and memory loss. The onset is slow and insidious, and it takes years to develop. Dementia is an irreversible condition.
- Delirium is an acute change in consciousness, characterised by fluctuating state of confusion, hallucination, inattention, and altered awareness. The onset is often fast and rapid. Unlike dementia, delirium is a reversable condition.
- Depression is considered a mood disorder. It is a persistent display of low mood and disinterest in what used to be enjoyed, and it alters cognitive function. Depression is a curable condition.
Common Misunderstanding
One of the prominent misconceptions or misunderstandings is that all three conditions are caused by ageing or old age, but in fact none of them is.
Delirium is often mistaken for dementia and vice versa as both involve confusion, and persons living with dementia can potentially experience an outburst of delirium.
For caregivers to manage these conditions, we must know the similarities and differences of these conditions.
Key Similarities
The following signs and symptoms are common to dementia, delirium, and depression:
- Cognitive decline: Persons living with any of these three conditions tend to face challenges in thinking coherently, concentrating on a single task, and notable memory loss.
- Behavioural changes: Persons with any of these conditions tend to withdraw themselves from social engagements due to communication difficulties, apathy, and loss of motivation in doing what they loved.
- Mood fluctuation: This is very common and visible in any of the three conditions. Oscillating moods commonly includes irrational irritability, fear, and sadness.
Key Differences
Knowing the differences could help caregivers make more appropriate decisions about treatments.
Manage Each of These Conditions
Whilst dementia, delirium, and depression share certain traits, managing them requires different approaches.
As dementia is a progressive condition, caregivers need to approach it with patience and develop a care strategy over time. Consistency, reassurance, and focusing on the person’s emotions are key to effective long-term care.
Creating a routine or daily schedule is crucial for persons living with dementia, as a cyclical routine can help them register and familiarise themselves with repetitive, daily tasks, such as taking a shower, having meals, and attending regular appointments. In addition, creating a cyclical routine can also reduce anxiety. At the same time, it is essential to make your home dementia-friendly by storing frequently used items, such as placing a bunch of keys at the same spot to minimise confusion.
Simplify communication and daily tasks can also help persons living with dementia. For example, you may want to keep your sentences short, simple, yet precise: “Do you want to wear the blue shirt or the green shirt?” instead of “What do you want to wear?”.
If your loved one becomes agitated or upset, try distracting them with a different activity or a favourite snack. Tap into their long-term memory, which often remains intact longer than short-term memory. Looking at old photos or reminisce about their past are good approaches.
Always remember that challenging behaviours are also a form of communication, indicating unmet needs like pain, boredom, or overstimulation.
Different from dementia, delirium often occurs as a sudden outburst. It is, however, a state of severe confusion that is potentially caused by underlying medical conditions, such as an infection, organ failure, dementia, or stroke.2 Managing delirium, therefore, requires identifying and treating underlying medical causes of the person with delirium.
It is advisable to remain calm when speaking to a person with delirium. Try to explain what is happening by using short, simple sentences. In addition, try to regularly remind persons with delirium of the date, time and where they are. This will help to orientate them and keep them calm.
Similar to persons living with dementia, persons with delirium need to be reminded of familiar faces and places to make them feel secure and feel at ease. Providing a quiet, peaceful space with the same caregivers can avoid overstimulation and anxiety. Try to maintain a regular sleep-wake schedule by keeping the room bright during the day and quiet at night. This also helps to orientate them mentally.
Managing depression involves a combination of professional help, lifestyle adjustments or changes, and social support; these include speaking with a doctor or therapist, maintaining social connections, exercising regularly, keeping a healthy diet, and breaking tasks into small, manageable ones. As reported in the Straits Times, one in four adults experience mild symptoms of depression and anxiety in Singapore.3
Unlike dementia, depression is a treatable condition. It is essentially a prolonged emotional distress that stems from eminent life-altering changes and challenges that cause emotion fluctuations.4 For example, when sadness is left unmanaged over a long period of time, it might spiral into depression. Depression can also be hereditary or caused by chemical imbalance, and psychological and environmental factors. Whilst depression might affect one’s ability to perform at work, triggers negative thoughts, affects eating and sleeping patterns, and impacts relationships, it is not a lifelong condition when properly managed.
Some common misconceptions of depression include “snapping” out of depression, depression only being a state of sadness, and only persons with a weak mind or character can get depression.
Conclusion
Managing dementia, delirium, and depression requires different sets of strategies and by knowing what these conditions entail will give you a good idea to tell them apart and manage them to avoid mismanagement.
- Department of Health Victoria. (2024, July 17). Differential diagnosis – depression, delirium and dementia. Health.vic. https://www.health.vic.gov.au/older-people-in-hospital/cognition-dementia-delirium-and-depression/differential-diagnosis-depression-delirium-and-dementia
- National Center for Biotechnology Information. (n.d.). StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK470399/
- Shafeeq, S. (2025, September 17). 1 in 4 adults in Singapore experience mild symptoms of depression, anxiety: Study. The Straits Times. https://www.straitstimes.com/singapore/community/1-in-4-adults-in-singapore-experience-mild-symptoms-of-depression-and-anxiety-study
- Johns Hopkins Medicine. (n.d.). Major depression. Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/conditions-and-diseases/major-depression
- Registered Nurses’ Association of Ontario. (2016). Delirium, dementia, and depression in older adults: Assessment and care (2nd ed.). https://rnao.ca/bpg/guidelines/assessment-and-care-older-adults-delirium-dementia-and-depression
- World Health Organization. (n.d.). Depression. https://www.who.int/health-topics/depression