Before one is admitted to the priesthood and many different religious orders, there is a psychological or psychiatric screening process to go through. If one doesnt pass, he/she isnt allowed to go any farther in the vocation process. Many who have wanted to be priests and nuns were turned down because of a vad psychological evaluation.
Why not do this for marriage as well? In theory, if you had this process you could save many people from divorce and anullment. You could also save people from marriages where one spouse has a problem with addictions of varying types and degrees and it can also identify potentially abusive and unfaithful spouses before marriage takes place. In the current process, you simply answer generic questions but rarely does the church say no to marrying two people unless there is something obviously and seriously wrong. Even then, they often can find a priest that would marry them.
The one benefit from a psychological evaluation before marriage is that the church can serve as the reason behind emotional relationships. The pastor of a church needs to protect his flock. How is a pastor being protective if he allows anyone to marry that goes through the marriage prep? Marriage is one of the most important decisions in life and it seems it would be only logical to make sure one of your flock doesnt get married to someone that is a major psychological risk. They wouldnt allow a person to become a priest or nun who failed a psych eval but why would they let married people do the same?
Sure, people will be mad that they were denied a marriage. However, isnt it better to not allow some to marry than to risk having a marriage that fails, needs to be anulled or is abusive? Those three lead many youth in those marriages to fall away from God. I think you would have stronger marriages and people would be more careful in who they dated and wed if there was a psychological evaluation. People with sexual and alcoholic addictions and would think twice about getting help and cleaning up their act before marriage.