There is a theory about the cause of his muteness saying that, the madness of his mother, the prince Ochi no iratsume might have affected, because she gave birth to him in a frenzied state of mind, since her father KURAYAMADA no Ishikawamaro (the prince's grandfather) was executed by Naka no Oe no Oji.
唖の原因として、母・遠智娘が父・倉山田石川麻呂（皇子にとっては祖父）を中大兄皇子に処刑され、悲しみのあまり狂乱した状態で出産したため、遠智娘の精神異常が皇子に影響したのではないか、という説がある。