The Messenger of Allah said: "Every divorce is valid except the divorce of the Ma'tuh person whose reason is overcome." (Da'if Jiddan)  

قَالَ رَسُولُ اللَّهِ ﷺ كُلُّ طَلاَقٍ جَائِزٌ إِلاَّ طَلاَقَ الْمَعْتُوهِ الْمَغْلُوبِ عَلَى عَقْلِهِ