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• Rules urge consultations with physicians
• Actual formula largely unchanged
• Number of exorcisms performed unclear
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VATICAN CITY (CNN) -- Blaming Satan for many of today's ills, the Vatican on Tuesday unveiled updated exorcism rules, along with a caution not to mistake psychiatric problems for diabolic possession.

The Vatican's first updated ritual for exorcism since 1614 tries to bring the church up to date with modern science and, for the first time, urges church-approved exorcists to consult modern medicine where needed. However, officials made clear at a news conference that the traditional belief in the devil was not optional for today's Roman Catholics.

"The existence of the devil isn't an opinion, something to take or leave as you wish," said Cardinal Jorge Medina Estevez, a Vatican official, adding that belief in Satan is a tenet of Catholic faith.

The devil "deceives men, making them believe that you find happiness in money, in power, in carnal desire," Medina said in presenting the revised rules. "He fools men by persuading them that they do not need God and that they are self-sufficient."

Except for some new formulas for priests, authorized by bishops, to read during exorcisms, the text is essentially unchanged. Instead the novelty appears largely in the cautions for determining if exorcism is warranted.

"The exorcist will decide with prudence" after consulting with spiritual experts and "if considered opportune, with experts in medical and psychiatric science," the new rules stress.

"First of all, he must not assume that those who are suffering from some illness, particularly psychological, are vexed by the demon," the guide says.

It says signs that a person is under the influence of the devil include speaking unknown languages and having physical strength disproportionate to a person's age or body.

The ritual of exorcism itself, outlined in detail in the booklet, includes prayers, the blessing and sprinkling of holy water, the laying of hands on the possessed and making the sign of the cross. It continues with appeals to Christ, the Holy Spirit and the saints of the church.

Then, the actual formula of exorcism begins.

The first is the "imploring formula," in which the evils of the devil are listed and God is entreated to free the possessed.

The second, more intense formula, is the "imperative formula" in which the devil is ordered to leave the possessed.

The imperative formula begins: "I order you, Satan ..." It then goes on to denounce Satan as "prince of the world" and "enemy of human salvation." It ends: "Therefore, Go Back, Satan."

The new text, an 84-page Latin-language book known as the Roman Ritual, is not yet available in other languages, but Cardinal Estevez said that was not a problem.

"The new manual comes into effect today in its Latin version," he said. "An exorcist can use the Latin version tonight if he wants because the devil understands Latin."

Vatican officials said they had no figures on how many exorcisms are performed, but major dioceses have their own exorcists. Estevez said he believed the number of true possessions today was "not that great, rather scarce," but that the amount of evil in the world left no doubt the devil was on the job.

Pope John Paul II has made it clear several times in his 20- year papacy that he believes in the existence of the devil. During a trip to Germany in 1987, the pope said the horrors of World War II, including the Nazi death camps, were proof that the devil was still at work.

The pope himself once performed an exorcism during his papacy, according to the memoirs of Cardinal Jacques Martin, the former prefect of the pontifical household.

Quoting the late cardinal's book, "My Six Popes," the Italian news agency ANSA said John Paul carried out the rite in 1982, driving out the devil from a woman who was brought to him, writhing on the ground.

The Associated Press and Reuters contributed to this report.