From the World Health Organization
EMF offers an alternative theory to hauntings and apparitions. Roll and Nichols provided research showing that houses with transient EMFs also have reported apparitions, unexplained footsteps, electrical disturbances and similar haunting phenonmenon.
Persinger, Tiller and Koren suggest that exsposure to EMF causes apparition hallucinations as well as influence mood, create depression and effect respiratory functions. In addition to EMF that is eletrically made, there is naturally occuring geomagnetic fields (GMF) and ion densities that may also have help produce these effects.
Studying environmental factors are very important. Similar conditions to EMF:
Vic Tandy also discovered that low sound frequencies such as 10 to 20 Hz can cause apparitional hallucinatory effects as well. This sound is below human hearing.
Also, in areas where there is relatively low humidity, people will feel much cooler because sweat evaporates quicker, an effect studied by Wiseman in his ongoing investigations of the Mary King's Close where a 10 percent change in humidity is present. This could be an explanation to "cold spots" that are often felt.
M.A. Persinger, S. G. Tiller, & S.A. Koren. "Experimental simulation of a haunt experience and elicitation of paroxysmal electroenephalographic activity by transcerebral activity by transcerebral complex magnetic fields: Induction of a synthetic "ghost"?", Perceptual and Motor Skills, 90 (2000). pp. 659-674
M.A. Persinger, ELF and VLF electro-magnetic field effects (New York, 1974)
V. Tandy & T. Lawerence, 'The Ghost in the Machine.", Journal of the Society of Psychical Research, 62 (1998) pp. 360-364.
W. G. Roll, & A. Nichols, 'Psychological and Electomagnetic Aspects of Haunts.' The Parapsychological Association 43rd Annual Convention: Proceedings of Presented Papers (2000) pp. 364-378.
Wiseman, Richard (2005). http://www.psy.hert.ac.uk/ghost/latest.html