Dementia: Definition, Symptoms & Care

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  • 0:07 Dementia
  • 1:13 Diagnosis
  • 3:22 Prichard's Stages of Dementia
  • 4:46 Causes and Treatment
  • 6:17 Lesson Summary
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

Whether due to Alzheimer's disease or drug abuse, dementia affects many people. In this lesson, we'll look closer at the symptoms, causes and treatment for dementia.


Rose's family is starting to think that there's something wrong with her. She used to be very smart and could talk for hours about growing up in the 1940s and '50s. But lately, she's been having trouble. She keeps forgetting where she put her keys, and once or twice, she's forgotten to turn off the stove. Not only that, her stories about growing up have become confused and jumbled, and often she can't remember details that she's repeated many times in the past.

Rose might be suffering from dementia, which is a disorder marked by a loss of cognitive functioning and memory loss. Dementia patients have trouble with both short-term and long-term memory. Forgetting where she put her keys or leaving the stove on are examples of short-term memory, while Rose's inability to remember details from her childhood is a good example of long-term memory. In addition to memory loss, dementia is often marked by losing problem-solving abilities, the inability to think in an abstract way and even personality changes. Dementia patients can become irascible and alienate the people who love them.


Imagine that you are a psychologist, and Rose's family brings her in to see you because they are worried that she might have dementia. In order to diagnose her, you go through a checklist of criteria for the disorder.

1. Multiple cognitive deficits

Cognition, or thought processes, must be impaired in multiple ways for someone to be diagnosed with dementia. Memory loss is one type of cognitive deficit present in dementia patients. In addition, patients might show problems with language, motor movement or planning and problem solving.

Rose obviously has some memory problems, but does she have any other cognitive deficits? When you talk to her, you notice that she is unable to understand abstract concepts. According to her family, this didn't used to be a problem. Because she has at least two cognitive deficits, she meets the criterion.

2.Impairment, distress and decline in functioning

The problems caused by dementia have to result in either the inability to carry on life as before or some sort of emotional reaction, like anger or sadness. In addition, the patient has to have a decline in functioning. This means that if someone had never been able to remember where they put their keys, it doesn't count.

But Rose's symptoms are new to her. She used to be really on top of things - she never forgot details, like where she left her keys or at what school she attended kindergarten. But lately she's been unable to remember those things, so they do represent a decline in functioning. In addition, she forgot to turn the stove off, which could put her in danger of burning down her house. That's a type of impairment, so Rose meets this criterion.

3.The symptoms cannot be explained by another psychological disorder

Sometimes, people can show signs of dementia because of another mental illness, like depression or delirium. But there's no evidence that Rose has any other mental disorder, so we can check this one off.

So, according to our checklist, Rose looks like she's suffering from dementia.

Prichard's Stages of Dementia

Descriptions of people who have dementia have gone back throughout most of history. In 1837, psychiatrist James Cowles Prichard first identified four stages of dementia. Though somewhat outdated, they are still the basis for how many people view dementia today.

Prichard's stages of dementia are:

1. Loss of memory - Prichard wrongly believed that in this stage people lost only their short-term memories. However, now we know that long-term memory loss is also part of dementia. But short-term memory loss is much more severe in dementia patients.

2. Loss of reason - This includes losing the ability to think abstractly, plan and execute plans and problem-solve.

3. Loss of comprehension - Many dementia patients gradually lose their language skills. They find it hard to understand others and to make themselves understood.

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