I remember hearing somebody (Douglas Rushkoff, I think) suggest that ADD-like behaviors might be an adaptation to a childhood in which one is inundated with aggressive, flashy advertising. Adapting to reflexively ignoring things that are designed to steal your focus probably affects your brain in the long term, much like meditating regularly can.
Interestingly, I find that this tends to affect the men of my family more than the women. My mom, sister, and wife don't seem to have this problem at all. While both my dad and brother all suffer from an inability to hold a conversation if the TV is on.
Of course, that's a pretty small sample set.