Priestly celibacy "was not a cause," she said.
She added later that the abuse scandal was not a compelling reason for the Catholic Church to lift its celibacy requirement for clergy.
Commissioned four years ago by the bishops from the John Jay College of Criminal Justice in New York, the report looked at the sexual abuse of minors by clergy between 1950 and 2010, a period during which about 5 percent of diocesan priests were credibly accused of child molestation. The cost to the nation's dioceses has been estimated at $2 billion.
The researchers found that more than 90 percent of the known cases had occurred before 1990. The incidence rose steadily in the 1960s, reached a peak in the '70s, and was declining markedly by the mid-'80s - correlating, Terry said, with a tumultuous time for American morality in general.
Within hours of its release, the report was stirring controversy. It took a largely sympathetic view of bishops who reassigned abusive clergy to parishes after counseling, and put little blame on the hierarchy for the problem of repeat offenders.
David Clohessy, executive director of the Survivors Network of those Abused by Priests, called the study inadequate and self-serving.
"This is one more effort by the bishops to say [clergy sex abuse] is ancient history and 'not our fault,' " he said. "To say it was caused by culture of a couple of decades ago is just ludicrous."
At the news conference, Bishop Blasé Cupich of Seattle, chairman of the conference committee that oversees sex-abuse matters, referred to recent grand jury allegations that the Archdiocese of Philadelphia had kept dozens of credibly accused priests in ministry. That, he said, would be an "anomaly" and not typical of most dioceses.
He conceded, however, that sex abuse "was sometimes very badly handled" by many dioceses over the years. "The shame of failing our children," Cupich said, "will remain with us for a long time."
