You gotta be kidding! That really is the topic of his doctoral dissertation? Specifically schizophrenia? My God, schizophrenia is an incredibly broad categorization. I sure know some unmanaged cases of schizophrenia where there is good reason to question whether the person is capable of the requisite free intent to contract marriage, secular or sacramental. But there are also many cases where schizophrenia is well managed and there is not reason to doubt requisite free intent. 

I am thinking in particular of a lovely couple whom I know who are happy as two peas in a pod. In fact, they have decided to merely live together, but, especially since the fellow is well known for his work around local parishes, there are many priests who would marry them in a heart beat.