For several disorders, there are now data to replace the interminable debate about the fundamental nature of these illnesses. 121 These occasionally vociferous debates 70 have generally been of an “either/or” nature: psychiatric disorders as collections of Mendelian-like, single gene disorders (multiple rare variant models) “versus” psychiatric disorders are caused by many common variants of small effects (common disease/common variant models). 15,122 Although we were initially agnostic 123 we now believe that the data support both positions.
