I wonder if there's a kind of positive feedback loop with one's own thoughts being mistaken for other entities' voices and the contents of the those thoughts.

For example, if you get a bit freaked out by suddenly hearing an unidentified voice in your head, you might fear it, and if you fear it and think it malevolent, you might start to imagine what type of things it might want or say and then by imagining it and simulating it, you essentially create the very thoughts this malevolent entity ultimately speaks to you but since you can't identify the source as yourself and it becomes the voice of this malevolent entity.