From past till today, there has always been a clash between the ideas of the extremes of the believers and non-believers of the “existence of ghosts” which certainly is doubtful. This article is not meant to disrespect other’s views and experiences related to ghosts and demons. One claims it to have a scientific reason and the other claims that the things that can’t be proved by science are labelled as non-existing by it.
In the center of our consciousness, there lies something that is too powerful to control which can command every part of our physiological faculty to obedience. This “something” here is nothing other than the human mind.
Most ghostly encounters are not visual, but rather consist of noises, smells, sensations, voices, cold spots, electrical disturbances such as lights switching off or on, and displacement or movement of objects. While there are several theories about ghosts (electromagnetic theory, parallelism,etc.), I would just like to shed light on some medical concepts.
Stimulation of some parts of brain leads to disturbance in various perceptions like vision, hearing, etc. leading to hallucinations. Some of the medical reasons for ghostly encounters are:
Schizophrenia is a psychotic disorder (or a group of disorders) marked by severely impaired thinking, emotions, and behaviors. Schizophrenic patients are typically unable to filter sensory stimuli and may have enhanced perceptions of sounds, colors, and other features of their environment. Schizophrenia have relatively high prevalence compared to other mental disorders. To learn about how schizophrenia leads to ghostly hallucinations: http://medchrome.com/minor/psychiatry/schizophrenia-summarized-article/
Medically, sleep paralysis is a neurology flaccid paralysis at sleep onset or on waking and in otherwise healthy person characterized by an inability to ‘kickstart’ the voluntary muscles, resulting in a transient ‘locked-in’ syndrome. It is associated with narcolepsy, Pickwick syndrome, sleep apnea, cataplexia and hypnagogic hallucinations. There is a high prevalence of sleep paralysis of about 40%. To learn about how sleep paralysis leads to ghostly hallucinations : http://medchrome.com/patient/sleep-problems/sleep-paralysis-alien-abduction-demon-or-physiological/
Hysteria is when someone has a very strong emotion that is unmanageable. Often, this means a very strong sense of fear. To learn about medical concept on demonic possesion and several mental disorders including hysteria: http://medchrome.com/featured/demonic-possesion-explained-medical-concept/
All of these conditions above have relatively high prevalence and are characterized by hallucinations and delusions. Also, most of the ghost reports are also the results of pranks. Besides, people have largely sold the idea of existence of ghost.
More theories about ghosts are available at: http://www.mysticalblaze.com/GhostsNature.htm