My mother keeps hearing people outside her window at night, but there's no one there. Could dementia cause this paranoia?

It's entirely possible that your mom has dementia that's causing this, but has she had any mental illness diagnosis in the past? Something that would cause these same symptoms? Has she ever been like this in the past, or is this new?

Unfortunately, when someone has dementia, the things they think they are hearing, feeling or experiencing seem very, very real to them. Sometimes it's impossible for them to rationalize something they see or hear, so they make up a huge, long story in their mind to justify it.
My grandmother was extremely demented in her later years and used to tell us someone was breaking into the attic through a window she had nailed shut, coming downstairs through several locked doors, getting meat out of the locked freezer, cooking it, eating it, washing the dishes and putting them away where she couldn't find them. All of this was to justify the fact that she had misplaced her favorite skillet.

I would recommend talking with your mom's doctor and seeing if a geriatric psych evaluation can be done to determine what's going on, and have her tested for any possible infections (like a UTI) to rule out any possibility of infection causing the change of mindset.

Sounds like your mom should visit her primary care doctor for a check up or a neurologist for an evaluation. Could be just age related dementia or a memory impairment. High blood pressure, not to fool with, can cause hallucinations. A uti may be the cause as well. A blood work up and urine test will show if there is any infection. Is your mom on any medications, especially a new one? A sleeping aid, some of the anti-psychotic meds can cause hallucinations or paranoia, even a simple antibiotic can do it. For peace of mind, get her checked out. If any meds are prescribed always watch for those dreaded side effects. The circle of life may bring on a caregiving role for us. We become more of a parent to our loved ones. I am caring for my elder brother with ALZ, I feel like a mom these days in lieu of a sister. What happened I ask many times! Wishes that all will be ok, helping our moms is the best, do it full steam! God Bless🌸

My Mom hallucinated a whole break in-even made them a snack!!! She had a UTI! Have the urine checked immediately to rule one out. The whole experience took at least 10 yrs off of MY life!!!

It would be a good idea to check to be certain there aren't any real sounds that would sound like what she's describing. For example, could there be a tree branch that hits or scrapes the side of the house? Are there any utilities, such as water running (or even a "babbling brook") or an HVAC system making noises that could be construed as conversation? If there is a real sound, it could be "amplified" in the mind of someone suffering from dementia.

My father in law who I am a caregiver for, would come out of the bedroom complaining that the guy who lived in the bathroom kept making noise, hollering woop woop, he lives with his wife alone in his home. I checked the bathroom and showed him no one there. I told him I would check outside, I went outside to check and found a squaril in a tree making noise in a tree outside the house by the bedroom. I chased it off and told him what it was. So try checking for any noise like a furnace /actually unit blowing or other noise that may not be a constant noise.

I do not have dementia and I have had the same problem that your mother appears to be having. There are times when I'm in bed that I can swear I hear what sounds to me like voices speaking very faintly or I will suddenly hear a loud thump but then I'm puzzled because while I heard the thump, my dogs who sleep with me, didn't....and they are very alert dogs. I thought either my house was haunted or I was losing my mind because I don't hear these things any other time except when I'm in bed trying to go to sleep. My doctor said it was an inner ear thing. Nothing serious, nothing fatal...some people have it and some never do. So I began using white noise in my bedroom. I have a fan that runs all the time and if that doesn't seem to do the trick, I turn on Pandora and it tunes out the noises. While I still hear it from time to time, it helps tremendously for me to know that the noises I'm hearing are all (literally) just in my head.

Dementia. Either organic or caused by a UTI. Get a geriatric doctor eval. He will do blood tests and a psych eval. There is medicine. The same thing happened with mom. First she started losing things and blamed us for stealing them. That was rough. We took her nail scissors, we stole her dental bridge, her nail file, her pad of paper. I was recovering from cancer. I was bedridden. She stood by my bed and badgered and demanded on and on until I got up on my skinny legs and looked for her items. This went on every day for a week until my husband said no more or you LEAVE. You will not do this to your daughter. Then it progressed to a man was stealing from her purse at night. Nope. A man was going to jump through the picture window and steal her purse. No mom. Not with the security cameras and all of us here with you. Nobody can even see your purse on the floor from the road waaaay out there. You are safe. She constantly repeated this spiel. Before we took her in with us she was driving. Ohhhh God. My husband found dents all over her car. Everybody is always hitting my car at church. Nope. We got a doctor eval, he yanked her driver's license and put her on medicine. The delusions are gone. We have different things going on now as her disease progresses. It was h*ll. Buy the book The 36 Hour Day. It will save your sanity.

My mom lives with me and does the same thing. I got her to sleep in another bedroom that was attached to mine and left a light on. She is now back in her own room and doesn't worry or hear/see as much. She doesn't even leave a light on anymore. She's 87+.

My mother has late-stage dementia and can barely hear when I am shouting in her ear, but she says she hears the dog trying to get in(we have no dog), hears music playing in the basement(we have no basement), and she says there are snakes in the bed and we have to check the toilet for snakes before she sits down. She has also been saying lately that there are bugs in her drink.

Read about Lewy Bodies syndrome. Causes hallucinations.