JFoster--

Put simply, it stunts your growth-- slows physical development, and you don't grow to be as tall.

Basically, in the chemical mayhem that is puberty, it's bad to introduce outside chemicals that fucks it up even more-- it can lead to weird chemical imbalance stuff, which leads to stunted growth, slower development (where it counts, too, if you get my drift) and even depression.

I don't mean to sound like DEA or anything; it's just that mid-puberty isn't the time to be fucking with your body chemistry.