Some girl who used to be pretty smart plays all the guys at school for a fool once she becomes hot by being a huge ditz.
Guy 1: "Dude, Sally was such a nerd back in 8th grade, but once she grew a rack she got really clumsy and all the guys love her for it."
Guy 2: "Yeah, she has a big time case of Jessica Simpson Syndrome."
The ailment of being very, very, dumb. Charecterised by random outbursts of an obsurd nature. Some signs may include but are not limited to the following
"Is Peanut Butter Dairy?"
"I always that an autobiography had to do with cars"
"Omg, Earthquake (Picks up cellphone)"
Omg, that gurl tottaly has jessica simpson syndrome, Poor michael.