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Difference between hallucinations, illusions, and delusions?

Take a look at the picture with this post. Are you looking at half a face, a full profile of a face, or both? This is an example of an illusion. An illusion is something that can be misinterpreted by your vision or hearing. Here is another example, something that happens all of the time in the real world. I walk into a darkened room, and before I turn on the light, I become immediately frightened by a scary shape in the corner. As soon as I turn on the light, I see that it is a large plant. Because of the shadows, I mistook the plant for a human figure.

Hallucinations, on the other hand, involve hearing, seeing, or feeling something that is not there. When I worked the emergency department years ago, I cared for an older woman who insisted there was an elf sitting on my right shoulder. She wasn’t frightened by it. In fact, she waved and talked to it every time I came over to her. By the end of the shift, I was starting to think that I had an elf sitting on my shoulder!

In people with dementia, hallucinations may arise from changes in the brain and the brain chemicals. Hallucinations may be scary, like seeing a stranger standing next to the bed. Or they can be comforting, like seeing and hearing young children playing in the living room. Sometimes the hallucinations may be more like vivid memories, such as when a person with dementia sees a long-dead family member from long ago.

Illusions happen when a person with dementia misinterprets actual objects in the room. A throw pillow is a cat. A garden hose is a snake. Poor lighting that creates more shadows can also create illusions. A shadow on the floor may be misinterpreted as a hole.

Delusions are false beliefs usually arising from fears. Sometimes, delusions occur early in dementia as the person tries to make sense out of a situation. For example, a woman with mild dementia always puts her house keys in the candy dish on the foyer table. Today, she places the keys inside a cabinet and immediately forgets that she did so. Because she ALWAYS placed her keys in the candy dish, she has multiple past memories of doing so. In her mind, she put the keys in the candy dish and now the keys are nowhere to be found. When she finally locates the keys in a cabinet, she decides that a family member is moving her keys on purpose. As more familiar items “disappear,” she may become very suspicious and have delusions of people stealing from her. Persons with dementia may have delusions of poverty (“I have no money in the bank”) and infidelity (“he is seeing another woman”). When I’m helping a caregiver dealing with delusions of poverty or infidelity, I often discover that these issues existed in the patient’s past. Perhaps the person with dementia experienced a time of limited resources or was married to a previous spouse who was unfaithful.

Dealing with illusions is the easiest. Good lighting and clutter removal often fix this. As for hallucinations, that depends. If the hallucinations are not causing fear or anxiety, we just go along with them. Some of my family caregivers have creatively dealt with more problematic hallucinations. One man saw someone sitting on a tree limb outside of his window, and he was upset by this. His son cut down the tree limb. No more hallucination. When I worked a night shift, I had a woman become upset because there was a strange man in her room. I took a mop from the janitor’s closet and “chased out” the intruder. She went back to sleep. If the hallucinations are creating a great deal of anxiety and fear, medication may be needed—but that is a conversation between you and the provider.

Delusions can also difficult to handle. I work with families on a case-by-case basis to come up with a strategy. I have found that keeping the person with dementia on a daily schedule, providing meaningful activities, and utilizing respite care services often “derails” the delusion.

Have you cared for someone with dementia who experienced hallucinations, delusions, or illusions? What did you do and did it help?


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Categories: Alzheimer's Disease Caregiving FTD Lewy Body Dementia Understanding Behaviors Vascular Dementia

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Dr. Rita Jablonski

Rita Jablonski, PhD, CRNP, FAAN, FGSA is a nurse practitioner, researcher, tenured professor, and former family caregiver. Her research and practice involve all aspects of dementia management; she is best known for non-drug strategies to address dementia-related behaviors.

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