ROME — Luca, 15, is rail-thin. When he hears the deliverance prayer, he flips over marble desks and screams in Greek like a scene straight out of a horror film.

Don Mario has had a troubled priesthood. He decided to receive counseling from a fellow priest last year after a malevolent "presence" drove him to harm himself.

The father of four-year-old Mattia has been organizing séances with friends. Mattia has not been himself ever since.

These are just three of the roughly 500,000 Italians who request an exorcism every year. Bishops from the Catholic Church enlist local priests for exorcisms in their dioceses but there aren't enough exorcists to meet the rising demand. The recent death of the Vatican's prominent exorcist, Gabriele Amorth, and the success of Liberami, a documentary on exorcism that won a prize at this year's Venice Film Festival, have shone a spotlight on a little-known "industry" that's rapidly growing.

"The devil's main advantage is convincing people he doesn't exist," explains Ildebrando Di Fulvio, an exorcist in the diocese of the central Italian city of Frosinone.

In the abbey of Casamari where he works, a constant stream of people arrive to ask Di Fulvio for help in "countering the strength of the devil." In his 50 years as a monk, he says he's witnessed "atrocious suffering" inside the millenary walls of this Cistercian abbey.

Many people believe they are possessed but few actually are, says Di Fulvio. They sense a strange presence and display unusual behavior but most turn out to be suffering from chronic depression or other mental illnesses, Di Fulvio says, adding that patients are often too quick to resort to exorcism as a solution. "Only in about 10 out of the hundreds of cases I've seen was the patient actually possessed," he says.

Di Fulvio lists the external signs that differentiate someone who's possessed from someone who's mentally ill: "A deformed facial expression; a cavernous voice; spitting out food or metallic objects they never ingested; speaking in archaic languages they don't know consciously like Hebrew, ancient Greek, Latin, and Aramaic; an unnatural physical strength they don't normally possess; and violent reactions to deliverance prayers and holy water."

Di Fulvio says that people often become possessed after participating in séances or Satanic masses, or after joining Satanic sects and cults.

Gianni Sini, a priest and exorcist in Olbia on the island of Sardinia, shares the story of four-year-old named Mattia who hasn't been himself. "The first time I met Mattia, we were in church and he kept kicking his parents. So then I asked him and his mother to go outside so I could speak to his father," says Sini.

Mattia's father "explained that every Saturday after working in his garden he would go to the countryside with his friends and conduct séances, just for fun. This is how little Mattia met the devil, because his father looked for him," says Sini.

Aldo Buonaiuto, an exorcist in the northeastern diocese of Fabriano-Matelica, says that 10 million Italians have consulted wizards, witches, fortune tellers, and astrologers at least once in their lives. "Most of them are charlatans who dupe desperate customers, but among them are some Satanists," he says.

Booming "industry"

Every exorcist carries a crucifix and holy water, always ready to recite the deliverance prayer to coax out demons from the possessed.

In Sardinia, Sini has performed thousands of exorcisms in his 30 years as an exorcist.

Even the Vatican has addressed the need for exorcists. Pope Benedict XVI once warned there was a need for an exorcist in each diocese in the world. Pope Francis frequently refers to the dangers of Satan in his sermons. But there aren't enough exorcists to meet the growing demand. There are only seven exorcists in Sardinia's 10 dioceses.

Elsewhere in Italy, the exorcism "industry" is booming. The number of exorcists in Milan has doubled, while an exorcism hotline was launched in Rome.

Exorcisms have traditionally been popular in poorer rural areas. Even today, 65% of people requesting exorcisms are less-educated women from central and southern Italy. But it's the other 35% that worries psychiatrists, as more people turn to exorcism. Many of these people are minors — 20 out of 100 people who claim to be possessed are underage.

Amorth conducted 50,000 exorcisms during his career, sometimes hundreds a day.

"Exorcisms aren't for the faint of heart and patients must go through a spiritual journey first," says Buonaiuto. "The first step is speaking with family members and psychiatrists to identify if it's a medical issue or not."

Demand for exorcisms goes beyond the Catholic faith — one young Muslim girl sought Sini after an imam she consulted advised her to speak to a priest.

Some, like Mattia, got rid of their demons quickly but it's not always easy. "Some exorcisms last years," says Sini. "Without a journey of faith, you cannot defeat Satan. It's those who believe that win."