We wish to make 4 points in response to the comments of Dr DeLisi. First, our intent was certainly not to provide "definitive" answers to the nosologic problems of psychotic disorders. No one study could hope to do that. Nor are we strongly advocating that others now adopt this system for clinical or research work. Our goals were more modest—to examine, using an agnostic but power statistical tool, the natural groupings of psychotic illness in an epidemiologic cohort of patients where both the subjects and their family members have been carefully evaluated. As we note in our article, such studies have been rare in a literature often more marked by speculation and controversy than careful empirical inquiry.
Kendler KS, Walsh D. A New Classification for the Psychoses?—Reply. Arch Gen Psychiatry. 1999;56(7):672-673. doi: