JGN, the interpretations of studies are based on assumptions and as such a sweeping statement about pranayama should be construed... If the person you mention is a psychology, it only means that he has studied the subject. It does not confer on him the authority on the same.
Moreover, the relation between the prana, the soul and the brain cannot be understood by mere bookish knowledge; it is "Sukshma Gyana" requiring more than mere application of theories and research.
And comparing them with drugs does not help; it means your understanding is limited only to that extent. The goal of pranayama is concentration and determination which cannot be found in schizpphrenics and drug addicts!
I think inferences rather depend on the perception of the individual...
