A condition found in couples. When apart the person in the couple is found to be tired and unwilling to go out. They would rather curl up at home and watch TV than go out clubbing. When they do go out clubbing they are often found sitting on sofas and are the first to go home. The also start not wanting to get too drunk.
person 1 "Dude wheres Michael?"
person 2 "Sitting on the sofa in the corner, serious case of relationship syndrome!"