Board Thread:Naruto Discussions/@comment-26636534-20180325094649/@comment-34752936-20180325134115

^It is stated in this wiki that if a victim is forced to experience a drastic passage of time in the fraction of a second Tsukuyomi is actually active, the stress on their mind would kill them, even if the genjutsu was a happy and peaceful one, such as when Itachi uses this technique to kill Izumi Uchiha by having her experience decades worth of time in a fraction of a second. It's also stated in the manga that, Itachi approached Izumi and placed her in an extremely powerful Tsukuyomi where she lived the entirety of her life in 0.000000001 billionths of a second. In her dream, she became a chūnin, retired from shinobi life to become Itachi's wife and raise their children, and lived to become eighty years old before dying of old age alongside Itachi. Because her mind was departed from reality in such a manner, Izumi collapsed into Itachi’s arms dying. Izumi thanked Itachi for giving her the life she wanted with him, even if it was a dream, and Itachi thanked her for loving him as she passed away.