Board Thread:Theories and Speculation/@comment-31099706-20170327120301/@comment-27924662-20170422021106

Experience experienced inside the Tsukuyomi are real. If Itachi stabs someone in the Tsukuyomi than brain will experience that pain regardless of body actually being in pain. If I remember correctly Izumi's case in the novel. She lived for 70 years and her brain sensed that she was going to have her natural death(at end of the 70 years), And it's when she actually starts to die that itachi breaks the jutsu. It's clear if itachi did try to completely kill someone in the genjutsu (for instance by burning him alive to his complete death, than most certainly that person would die).