Grisi Siknis (Crazy Sickness)

"One day at school, I felt giddy, and found it difficult to breathe," she said.

"Then, I saw something coming towards me - a kind of black man or a dragon that entered me and possessed me."

Three other girls were affected the same day at Anadina's school, where Reverend Harold Dixon is headmaster.

He has witnessed many attacks of Grisi Siknis.

"They get giddy and they faint and fall to the ground," he said.

"Then, they start hollering and they hit their heads on the wall or desk. They have an extra strength.

"You have to have five or six people to hold down one girl."

Lille, France, 1639
Mackay (1852, 539-540) reports that in 1639 at an all-girls' school in Lille, France, fifty pupils were convinced by their overzealous teacher that they were under Satanic influence. Antoinette Bourgignon had the children believing that "little black angels" were flying about their heads, and that the Devil's imps were everywhere. Soon, each of the students confessed to witchcraft, flying on broomsticks and even eating baby flesh. The students came close to being burned at the stake but were spared when blame shifted to the headmistress, who escaped at the last minute. The episode occurred near the end of the Continental European witch mania of 1400 to 1650, when at least 200,000 people were executed following allegations of witchcraft.

Here's something...

Apparently several incidents of placebo-induced hexs from witch doctors where people convince themselves into death when there's not anything physically wrong with them

http://www.newscientist.com/article/...acks-body.html

Have there ever been instances of people claiming to be possessed who didn't belong to a highly religious community that believes in possession?

I think that, especially for young people, it gives them a chance to throw off the tight constraints of such controlling religions for a brief time. They may believe in it, but the overwhelming subconscious desire to act freely may induce them into expressing a psychosomatic symptom of something they believe could happen. Just a guess.