Do you think aliens in ufos have visited Earth? (And all things UFO)

I remember seeing a documentary about a psychologist who went through the most plausible sightings of 'greys' and shortlisted some where the sighting was hard to refute and the person who reported the sighting didn't really have anything to gain in terms of notoriety or money.
Some of these people were successful in business/society and were actually reticent about cooperating. After analysing them he became convinced that they were neither lying nor disturbed and genuinely believed they saw something 'alien'.
He arranged for brain scans and neurological tests of these poeple to see if there was something in their physiology which might explain it.
If I remember correctly all but one had very slight epilepsy which had not previously been diagnosed.
He concluded that what they had actually experienced was a very mild fit in which their brain was being overwhelmed with light and distorted shapes. He believed the greys they saw were their children / family members who had come to see if they were okay whilst they were confused and disorientated from the epilepsy.
This would explain why many people do not report being harmed by greys and why some are reported as small in size like children.
If true it also goes to prove that some who come forward are not necessarily weirdo publicity seekers or nut jobs but people who truly believe they have had an alien encounter even if they probably have not.
It might also explain why people have previously reported seeing ghosts as intense light shapes.
Worth considering.