haunted houses

Haunted houses were more common, back then. I think it was because in the generation before electric lighting, houses used gas. 

Burning gas gives off waste products. Most importantly, carbon monoxide. This stuff can make you lethargic, paranoid, and can even cause hallucinations of voices and visions. 

Also, ghosts love the stuff. If you've got a carbon monoxide leak, that's like putting out catnip, but for ghosts.