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Delusions, hallucinations, and generally misinterpreting the world are not uncommon in dementia. Here are some of the reasons they happen, and what can be done about them.

I lived with my dad, who had vascular dementia related to Parkinson's disease, for 10 years. One day I came home to find him busily installing a kitchen faucet in my bathroom sink.

"Your mother told me I needed to do this," he offered.

"But Dad, if you didn't do things just because she asked you when she was living, what makes it so urgent when she's not here any more?" I asked.

Dementia often leads to delusions. These are false beliefs a person firmly holds despite evidence to the contrary. Delusions defy conventional understanding of the world. Dementia also often leads to hallucinations. These are sights, sounds, smells, touch, and smell that don't correspond to the physical world. When these hallucinations "speak" to the person who has them, they may be followed with delusions.

What causes delusions in dementia?

The way researchers understand delusions work is terms of what is needed to understand the world the same way most other people do. There are two steps in establishing beliefs. One is understanding your own perspective. You need to be able to plug in to your own way of looking the world. The other is understanding how other people view the world. This involves consideration of their experiences, prejudices, preferences, and whether or not they are expressing themselves truthfully.

Different kinds of dementia result in different kinds of issues with these two processes. People who have frontotemporal dementia have difficulty understanding their own beliefs.

My dad, mentioned earlier, lost his filter that helped him decide whether someone had to be alive to ask him to do chores around the house. He had intact abilities that allowed him to drive to the hardware store, buy a faucet, and install it, but not to reconsider whether or not my mother had actually reappeared from the afterlife out of concern to put kitchen faucets in the guest bathroom. He retained many of his social skills, but he lacked a kind of self-awareness that would enable him to realize he had been hallucinating and forming a delusion on the basis of that hallucination. (It is possible to have hallucinations and realize you are hallucinating.) 

Many people who have Alzheimer's have difficulties with the social aspect of belief, the ability to discern whether people who agree with you, or disagree with you, are right, wrong, or making stuff up. One way of understanding how this works, although it is exaggerated, is a game played with children called "got your nose." An adult places his or her hand near the child's nose, and says, "Got your nose!" The appropriate response from the child is "No you don't! Ha ha ha," not "Give me my nose back, d*mn it." While the reaction in Alzheimer's usually isn't quite this lacking in nuance, it involves loss of confidence in one's own beliefs and a severe susceptibility to being lied to.

What causes hallucinations in dementia?

The two processes of understanding the world occur in two different parts of the brain. Hallucinations, on the other hand, are more global. Most reported hallucinations are visual, seeing things that the rest of us maintain aren't there. Hallucinations can involve all the senses. It's possible to hallucinate the smell of fresh laundry or the sound of a bassoon, for example. Hallucinations are sometimes comforting, sometimes scary, and sometimes, well, just odd.

Hallucinations are a more common feature of kinds of dementia that involve the formation of Lewy bodies. These are tiny tangles of malformed proteins inside nerve cells. Lewy bodies are observed in Lewy body dementia and Parkinson's. A majority of people who have these two conditions will experience hallucinations at some point in their disease. People who have other major neurocognitive disorders can also experience hallucinations, but they don't occur as commonly.

What can be done about delusions, hallucinations, and false beliefs?

There are medications that reduce the frequency of delusions, hallucinations, and false beliefs. The go-to medication in the United States for these psychological manifestations of dementia is Seroquel (quetiapine). A nursing home may easily get a PRN (as needed) order to dose Seroquel and turn off the crazies. But that's not always a good thing..

Delusions and hallucinations aren't just false beliefs. They are false believing. They are part of a process through which someone who has dementia tries to make sense of the world. If you turn off that process, the patient can develop a sense of hopelessness, a complete lack of control. I can't say that I had this all figured out when my dad was putting kitchen faucets in the bathroom and playing pinochle with his three dead brothers (and losing to them, I found that particularly disturbing). But I tolerated as much as did not clearly interfere with safety. If Mom had told Dad to drive down the wrong side of the road, then it was time to take away the keys. There came a time for nursing care. I was opposed to giving him Seroquel (and outvoted on that). We do not always know what we need to know when we need to know it.

It's important not to overmedicate for hallucinations and delusions. One medication at a time is better than multiple medications with multiple side effects and unpredictable interactions. Medicate for safety, not for convenience.

But what can you do besides just asking stern questions about medications, that nursing homes and doctors may insist be taken? 

Consider that there are two sources of false beliefs. One is some random "crazy" thought that for some reason your loved one has taken into their head. The other is not being able to sort out the veracity of what other people tell them.

Don't feel that you have to be the thought police. You don't have to make sure someone has right beliefs all the time. You just have to make sure they don't endanger themselves or someone else. What is dangerous may be very different in different situations. Going back to my own experiences, I could stare down my father and deal with him when it was just him and me. But there was a point he simply was not safe for himself or other people in public.

When the problem is misunderstanding other people's beliefs, insulate the person you are caring from them from influences they can't handle. That doesn't mean that these people who have to be excluded from their lives are "bad." It just means they present more than can be processed by a diseased brain.

  • Chiu PY, Hsu MH, Wang CW, Tsai CT, Pai MC. Visual hallucinations in Alzheimer's disease is significantly associated with clinical diagnostic features of dementia with Lewy bodies. PLoS One. 2017 Oct 31.12(10):e0186886. doi: 10.1371/journal.pone.0186886. eCollection 2017. PMID: 29088240.
  • Friedman JH. Parkinson disease psychosis: Update. Behav Neurol. 2013 Jan 1. 27(4):469-77. doi: 10.3233/BEN-129016. Review. PMID: 23242358.
  • Le Bouc R, Lenfant P, Delbeuck X, Ravasi L, Lebert F, Semah F, Pasquier F. My belief or yours? Differential theory of mind deficits in frontotemporal dementia and Alzheimer's disease. Brain. 2012 Oct.135(Pt 10):3026-38. doi: 10.1093/brain/aws237. PMID: 23065791.
  • Photo courtesy of SteadyHealth.

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