In a new twist to an very old phenomenum a research group in New York are looking at the possibility that the chances of someone seeing a ghostly image might be increased if that person has been inhaling mould and other dust often found in the air of the older buildings often associated with spirit sightings.
On the face of it this doesn't seem very likely to be much more than an exercise in publicity to raise interest in the psychological effects of breathing in mould spores. We do not know much about what the phycological effects of inhaling mouldy dusts might be and what doses might trigger hallucinogenesis - there is a clear suggested link with fungi that are know to be psychoactive but in those cases the fungus is eaten in far larger quantities that are usually inhaled. Perhaps this study will tell us something about the effects of much lower doses of similar compounds?
However the group appear to be just looking at the range of micro-organisms found in such a building rather than directly looking for the presence of metabolites. This type of study has been done many times over the last ten years but none have focused around haunted buildings - the ERMI ratio of the range of micro-organisms in a damp home compared with the range in a dry home tells us something about how damp a home might be so perhaps a ratio comparing haunted homes with non-haunted homes might be equally informative?
We do know that old damp buildings accumulate moulds and other microbes in dust that might be airborne when someone is moving through a building - but then again many sightings of ghosts take place outside rather than inside building so this cannot be a complete explanation for the phenomena.