Marie McClellan told me that she was 15 when she first thought a demon was inside her. A blossoming Canadian girl with dyed green hair and an oversized flannel shirt, she was attending rehearsal for an Easter play at her evangelical church in New Brunswick when she began to feel a fear crawling under her skin. As an actor playing Jesus was being nailed to a cross with fake blood dripping from his hands and face, McClellan started breathing rapidly and violently scratching herself.

Three years after that initial incident, McClellan still believed a demon was tormenting her. One night while she was working as a church camp counselor just outside Sussex, she felt it take control of her body once again. She told me that she began to rock back and forth, mumbling to herself. A prayer circle of church-camp counselors and pastors enfolded her and attempted to perform an exorcism, which she said only intensified her terror.

Finding no relief from the pastor's prayer, McClellan told me that she began cutting herself in the months and years that followed, finding comfort in harming this body she thought was inhabited by a demon.

McClellan didn't know this pastor (he was from another church), but she believed him. He kept her pinned to the floor for a few minutes, praying over her. After he left, she never saw him again.

"Have you ever played with a Ouija board?" he asked. McClellan nodded. The pastor explained that she had a demon inside of her (likely angered by the site of a real-life crucifix). It was a concept that filled her with horror and a kind of psychological detachment from her own body.

"I didn't know what was happening to me. I just knew I had to get out of there," she told me over the phone, as she reflected on that harrowing night in 1995. Her behavior was so frantic that she was approached by a pastor, who she said pinned her arms to the floor. His touch only caused her more terror—a common sign of demonic possession.

Such was the case with Kyong-A Ha , a 25-year-old woman who sought help with her insomnia via spiritual guidance from Jesus-Amen ministries. Ha was diagnosed as possessed by a demon, then restrained and beaten to death during her six-hour exorcism in Emeryville, California, in 1995. Church leader Jean Park later told police "the damage to Ha was done by demons."

Throughout history and in faiths beyond just Christianity, demonic possession has been a common misdiagnosis for all kinds of ailments. In retrospect, it is often revealed that many of these people suffer from disorders like schizophrenia or epilepsy. Regardless of the true underlying medical issues, some religious figures perform exorcisms today like the one McClellan went through. While McClellan's exorcism left her with lasting psychological damage that took years of therapy to overcome, exorcisms can be even more disastrous and potentially fatal. In recent years, stories of exorcisms involving people being beaten , poisoned , stomped , and starved to death have made global headlines.

Today, McClellan no longer believes she was possessed by a demon. Instead, medical professionals have deduced that she was suffering from an anxiety disorder, which was worsened by the suggestion of demonic possession (leading to the cutting) and later the experience of being restrained in an exorcism.

"Someone was always praying over me. A lot of it wasn't in English. Everyone was speaking in tongues. They were grilling me to confess my sins, and as each sin was confessed they called upon the holy spirit to drive that demon out of me."

An exorcist himself and former state senator from Colorado Springs (arguably the evangelical capital of the US), Klingenschmitt feels that the practice has been misrepresented by the media. "In my experience, modern exorcisms are very gentle, very common, and very liberating," he said to me over the phone. "We in America have a jaded portrayal of exorcisms through the media and Hollywood. It's not like it is in the movies."

Known for their belief in "supernatural warfare" (the idea that angels and demons are in constant battle for our souls and bodies), evangelicals like Gordon Klingenschmitt say engagement in any kind of sin can be an invitation to possession. Which means pretty much everyone is a potential candidate for exorcism.

The perpetrators of these crimes are often isolated evangelical groups who aren't plugged into the same infrastructure of oversight that the Catholic church has.

With these filters in place, Catholic exorcisms slowly became more and more scarce over a period of centuries. However, in the past few decades, the practice was revived in popular culture, where it has been associated most strongly with Catholic priests. This has helped contribute to a resurgence of Catholic exorcisms around the world. Though instead of church leaders diagnosing people as possessed by demons, priests today are inundated by people diagnosing themselves, and insisting on being given an exorcism.

Catholic priests typically have a different approach than evangelicals. They learned their lesson centuries ago that just because a person loses their appetite, or scratches at their skin, does not mean that they are in need of a (potentially violent) exorcism. Today, it is standard for someone to be evaluated by a mental health professional before an exorcism by a priest is even considered (a process McClellan could've benefitted from).

This phenomenon was recently documented by French newspaper Le Monde, which reported that the US went from having 12 noted exorcists in 2000 to 85 in 2014. In 2014, the Vatican formally recognized the International Association of Exorcists, a collection of Catholic priests performing exorcisms around the globe, and began hosting its own courses on exorcisms. Last year, the group had 150 priests in attendance. This year it ratcheted up to 250. Not to mention the Vatican has recently adopted a policy to have at least one exorcist in every diocese to meet the increasing demand.

According to Le Monde's report, those requesting possession come from all social and class backgrounds, though "75 percent are women—a very large majority of whom have been victims of sexual abuse (rape, incest, etc.)" This demographic of abused women is also reflected in the subjects of Libera Nos (Deliver Us), an upcoming Italian documentarian directed by Federica Di Giacomo that shows how exhaustively inundated Catholic priests are from parishioners demanding exorcisms. This phenomenon of battered women seeking exorcisms could suggest that many of those who believe they are victims of possession could really be suffering from psychological trauma.

"For a lot of people, when the priest gives an explanation for their problem, it gives a name to it, and some of them say they were delivered," Di Giacomo told me over Skype. "In Italy, there is little opportunity to go to a psychologist for free, and many just give them pills. They tried New Age, they tried Ayahuasca, but the priest is from their own culture, and it's real to them."