Little ones are designed for survival, so they wake easily to co-regulate themselves with their mother. Sears explains that infants who wake up alone feel startled as they search for their mother. Increased adrenaline and heart rate lead to crying and difficulty going back to sleep. Sears explains that infants who co-sleep rarely cry during the night and have less nighttime anxiety. As adults, they experience fewer sleep disturbances than adults who slept alone as infants.

