The following video is actually quite sad, and you can feel for the woman's family. The line between mental illness and religious fervour can be hard to distinguish, and possibly both are mutually reinforcing.
From another thread:
From the article:This may help explain what religious people feel:
God on the brain: is religion just a step away from mental illness?
God is an artefact of our evolved human minds, and that visions are symptoms of neurological abnormality. As well as Moses, experts are intrigued by St Paul, who famously encountered God in a blinding flash while on the road to Damascus, and St Teresa of Avila, who heard voices and is widely thought to have exhibited signs of schizophrenia.
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As soon as our brains became sufficiently evolved to embrace supernatural ideas, Boyer suggests, religion spread like a cerebral virus.
And also:
http://www.autoadvic...raindisease.htm
Tertiary Neurosyphilis
Tertiary neurosyphilis, is the most interesting form of syphilis from a cultural point of view. Just before the onset of paralysis, the sufferer is beset with delusions of grandeur, a sense of understanding everything, a sense that he is on the verge of some monumental discovery which will forever change the course of history, as well as a sense that some divine electricity is coursing through his veins.
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The syphilitic experiences, in Hayden’s words,
"episodes of creative euphoria, electrified, joyous energy when grandiosity led to a new vision. The heightened perception, dazzling insights, and almost mystical knowledge experienced during this time were expressed while precision of form of expression was still possible. At the end of the 19th century, it was believed that, in rare instances, syphilis could produce genius."
Despite all that, I'd be very hesitant to attribute general religious belief on mental disorders. Extreme examples where schizophrenia, disease, or other problems cause people to hear voices or think they are God are the exception. For most people, religion is simply the default option, a societal norm and a part of the environment, a comforting delusion to give life purpose and meaning.