Does it seem that the number of traumatic brain injuries, genetic defectives, and freaks of nature is over-represented in the Jihadist population?
Inbreading.
Al Qaeda's web site promo:
Give me your blind, wretched brain inflected masses, your lame, your lame-friggin'- brained, your dufus's, your plain and simple Lindh-y limp wristed fooly boys, your ugly monkey looking motheroos, your can't shoot straight gang, your dumb-sh!t shoe bomber wanna-bees that can't figure out a lighter, etc, etc, etc
not nearly as much as in the Xlinton administration.