A system and method for real-time alteration of media content based on stress monitoring is disclosed. A computer system present a single media content item in two distinct content streams to a first and second user. Using sensor generated data the computer system measures at least one user response indicator for the first and second user and estimates a stress level for the first and second users. The computer system determines whether the estimated stress level for the first user exceeds a first predetermined stress threshold. In accordance with a determination that the estimated stress level for the first user exceeds a first predetermined stress threshold the computer system alters the first stream of the presented media content item to modify the particular portion of the media content item associated with the estimated stress level for the first user.