WASHINGTON — Researchers commissioned by the nation’s Roman Catholic bishops to analyze the pattern of clergy sex abuse over decades have concluded that homosexuality, celibacy and an all-male priesthood did not cause the scandal.

The report from the John Jay College of Criminal Justice in New York said about 44 percent of the known abuse cases involved priests who were ordained in the 1940s and 1950s, at a time when seminaries did not properly train them to live a celibate life. These men were not equipped to withstand the social upheaval of the 1960s, which was a time of an increase in sexual deviancy and a spike in crime in society at large, the authors said.

The full report is the last of three studies commissioned by the U.S. Conference of Catholic Bishops as part of child protection reforms adopted in 2002 at the height of the abuse crisis. Dioceses nationwide have received allegations from more than 15,700 people against about 6,000 clerics since 1950, according to reports John Jay and others compiled for the bishops.

The debate over what caused the crisis has fallen along ideological lines, with liberals blaming mandatory celibacy or the lack of women in positions of authority. Conservatives pointed to gay priests, since the majority of known victims were boys.

The John Jay researchers, however, said the offenders chose boys mainly because the clergy had greater access to them. According to the researchers, abuse cases peaked in the 1970s, then began declining sharply in 1985, following a similar trajectory for the rate of abuse in society at large.

The bishops hoped the results of the study, first reported by Religion News Service, would help them better identify potential offenders. The researchers, however, said they found no “psychological characteristics” or “developmental histories” that distinguished guilty priests from clergy who did not molest children.