This is a useful finding because among many issues the bishops must grasp before they suggest ways to keep young people engaged in their faith is to understand why so many of them have fallen away. That question is sure to consume considerable time when bishops from around the world descend on Rome in October.

The same question will be prominent later this month during a pre-synod meeting at which hundreds of young people from dozens of countries, including two representatives from Canada, will gather for six days in the Vatican. They’ll be encouraged, in the words of Pope Francis, to be voices of faith, but also of doubt and criticism. Their important role is to give the bishops a respectful earful so the bishops can be more productive in October.

Breaking down a complex issue into three categories, as was done by the U.S. study, may be oversimplifying matters. But to regard disaffected Catholic youth as either injured, adrift or dissenting is a useful starting point.

The injured are those who have experienced a sudden crisis of faith due to a family or Church situation.

These can range from parental divorce, a death in the family or some type of negative ecclesial experience.

Drifters are those who gradually disconnected due to difficulty living by the rules and rituals of the Church. For them, it might be a question of finding relevance and often they are influenced by the example of parents whose faith may be uncertain.

The difference between them and dissenters is that dissenters actively resist certain Church teaching, particularly on social matters such as same-sex marriage, gender theory, contraception and abortion. They tend to reject Church authority and often distrust an institution they regard as judgmental.

None of this is good news. The three categories may differ but they produce the same outcome: someone becoming disengaged from the Church. Once gone, persuading a return becomes a major challenge.

So a close examination of this problem is long overdue.

Events such as the international celebration of World Youth Day can leave the impression of a vibrant Church.

The reality, however, is less rosy, particularly in Europe and North America, where young people are falling away from Church and avoiding religious vocations and marriage.

The bishops have much work to do. But their first task is to listen carefully to the youth that will be in Rome this month. They represent the future of the Church but they need to be heard now.