This article strikes me as shoddy. It seems to be saying that this phenomenon started with Elvis, and suggests that girls do it now because they've seen other people do it. This comment on the article was pretty enlightening:

"In the year 1842, five years into the proper Victorian Era, and that's when Lisztomania swept the land. [Hungarian musician Franz] Liszt was 31 years old the year he landed in Berlin. He'd established a new mode of performance — the solo piano recital — and new kinds of non-narrative music that people compared to musical poetry. He also developed a violent playing style that broke strings and sometimes brought down entire pianos. The Berliners were enchanted. At his concerts, they worked themselves up to screaming, fainting ecstasies. Women followed Liszt down the street and picked up his old cigarette stubs, made bracelets from his broken piano strings — and tried to rush him en masse, and pull out or cut locks of his hair. The craze spread outward from there, getting Britons and Italians as Liszt moved around"

http://www.neatorama.com/2012/08/27/Music-Idol-Causes-Women-to-Swoon/

After reading that, it almost seems as if it's a natural human reaction! It seems strange to me, though. I've never seen that happen at a concert, nor have I wanted to do it myself. I mean, I shout out between songs to show appreciation, but to continually scream for an hour and a half sounds pretty weird.