VATICAN CITY (CNS) — A newly expanded compendium of visions of the Virgin Mary shows how the very idea of such apparitions has been met with skepticism and preoccupation within the Church, from early Christian times to the present.

Experts in Mariology presented the Italian edition of the Dictionary of Apparitions of the Virgin Mary, translated from the original 2007 French publication with the addition of some 150 new entries, at a news conference near St. Peter’s Square Dec. 13.

The 1,600-page volume lists more than 2,400 claims of people who over the centuries alleged to have seen Mary, as well as the consequences of such announcements. Only 15 of these have been officially recognized by the Church, a confirmation of the caution with which the reports have historically been received.

French Father Rene Laurentin, a co-author of the book, acknowledged the diffidence regarding such claims.

“The apparitions are not seen with the most benign eye by the Church,” he said, citing the difficult histories of even the most popular and accepted visions. “Apparitions are the least scientifically studied, the most hidden and most controversial of all theological subjects.”

The co-author of the book is journalist and historian Patrick Sbalchiero. It is published by Edizioni Art, a publishing house associated with the Legionaries of Christ.

Father Laurentin, an expert on the sanctuary at Lourdes, France, and other shrines inspired by Marian apparitions, said in the introduction to the book that he had been working for more than 50 years on the dictionary at the request of bishops and the Congregation for the Doctrine of the Faith. The goal, he said, was “to put to rest the many misunderstandings and confusion” surrounding visionary claims.

But new diagnostic techniques and modern psychology can help at least in eliminating the claims of people suffering from hallucinations or other pathologies, the experts said at the presentation.

Dr. Tonino Cantelmi, professor of psychiatry at the Pontifical Gregorian University and president of the Italian Association of Catholic Psychiatrists and Psychologists, said advanced neuroimaging tests such as the PET scan demonstrate that a specific part of the brain shows activity during what could be described as ecstatic experiences.

In the past, Cantelmi said, psychologists and psychiatrists tended to believe that all such alleged experiences were psychological in origin. Researchers are now saying, he said, “that there may be something that is not psychologically explainable.”

Father Laurentin said that studies in California and Italy using electroencephalograms showed that visionaries were neither asleep, dreaming, hallucinating or having seizures during their experiences, but that their brains were in a normal state.

Father Paolo Scarafoni, rector of the European University of Rome and professor of theology at the Legionaries of Christ’s Pontifical Regina Apostolorum University, said that even though the Church must be cautious in its approach to claims of apparitions, the alleged visions should be respected “because they involve millions of people.”

Even those apparitions that have not been officially recognized by the Church are celebrated in shrines around the world by millions of Catholics, he said, and “the door should not be closed on those, but should be studied slowly before final judgment is made.”