Post-traumatic stress disorder affects at least 7 percent of Americans. Whether from combat or traumatic events, the effects of invisible wounds are hard to "see." Staff Sgt. Billy Caviness walks us through his daily struggle, like the meds he has to take every day (:55), how deeply his physical wounds affect him (3:18), and the revelation that probably keeps him sane (6:54). But make sure you stick around until the end for a big surprise that I didn’t see coming (8:08).