Or, rather, is this our minds (and then our bodies) playing games with us? Or is it all about belonging? 

Check this article “What happened to the girls in Le Roy?” from the March 11, 2012 New York Times Magazine.

A teaser-quote:

How could one person’s illness be reflected in another person’s neural pathways, playing a trick on consciousness, convincing the host that it originated in her own body? In the last decade, scientists have begun to explore the concept that regions in our brain once thought to activate only our own activity or sensations are also firing what are known as mirror neurons when we witness someone else perform an action or feel a sensation. Mass psychogenic illness could be thought of as the maladaptive version of the kind of empathy that finds expression in actual physical sensation: the contagious yawn or sympathetic nausea or the sibling who grabs his own finger when he sees his brother’s bleed.

And another:

… to believe in mass hysteria is to believe in the power of the mind to convince itself of almost anything.