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Imagining my sister wants to set fire to her house or stab her!


New member
Sep 17, 2020
My mother, who is 92 next month and has been diagnosed with Alzheimer’s, not only believes someone comes into her house and wants continually to change the locks, she is always saying my younger sister wants to stab her and she has seen her standing there with a knife, or she is going to set fire to the house. Has anybody else experienced this? She also cries a lot. Do you think anti-depressants would help her?


Volunteer Host
Apr 1, 2016
Hello @Madwin and welcome to Dementia Talking Point

Sadly this is common and it’s definitely worth getting in touch with your mother’s GP to see if anything can be prescribed to lessen her anxiety.

Instead of saying that your sister wouldn’t do these things perhaps saying that you’ll sort it out/have a talk to her/ get the police to talk to her will help with your mum’s delusions. I found that my dad could be soothed by the thought that I was dealing with whatever was upsetting him.

This may help give you some ideas for how to talk to your mum:



Registered User
Feb 25, 2014
South coast
It is, sadly, quite common.
My mum thought that her ex-cleaner was coming in and stealing things from her (in reality she was moving things around herself and putting thing things in "safe places" and then forgetting that she had done so) and then she started telling neighbours that I was abusing her and stealing from her as well.

In mums case she became quite paranoid and it wasnt until she moved into a care home (because she was no longer safe at home) that all these delusions went. Im sure that it was due to anxiety about being on her own at home. She would not see doctors or take medication, so I dont know if antidepressant/anti-anxiety medication would have helped.


Registered User
Nov 4, 2014
My mum had an obsession with locks, she thought people would break in at night and attack her, she was prescribed a low dose of Risperidone which helped enormously. We also fitted a bathroom style lock on her bedroom (the type that can be unlocked from the outside with a coin or screwdriver) which made her feel more secure at bedtime, she never did realise it could be opened from the outside even though I brought her a cup of tea every morning.

Grannie G

Volunteer Moderator
Apr 3, 2006
Hello @Madwin

Good advice so far and I endorse that from @Bunpoots. Whenever my husband had an irrational fear I told him to leave it with me and I would sort it.

I also agree to seeking medical advice. medication can be helpful at times like these.


New member
Sep 17, 2020
Thank you so much for all your helpful advice. I have an appointment to speak with her GP later today.