Yeah, JWs and the good, old, demon stories. I used to hear them a lot. Years and years back there was a woman in the KH who insisted that demon was sitting on her chest at her sleep and she was so scared that she felt asleep on her love seat. She used to complain in the KH that she felt something heavy sitting on her and was freaking her out. Later she was diagnosed with some kind of cancer in the lung and she eventually passed away. She also claimed that the demon was following her everywhere as she had this condition in any places where she went.
I agree with Lisa, that it is widespread delusion among JWs. However, I would not underestimate medical condition like mental issue, dementia, or starting of Alzheimer where one JW claimed that demon was misplacing his stuff.