This is an interesting article about how Post Traumatic Stress Disorder not only affects humans but can also be seen in animals.  Not nearly as much research has been done on how PTSD affects animals, but some animal behaviorists believe that dogs experience similar forms of the disorder. 

Gina, a two year old dog, did a six month tour in Iraq and came back showing similar symptoms to her human counterparts.  For the past year people at Peterson Air Force base have been working on rebuilding her confidence and getting her back to her old self.  Thanks to all the hard work she has made a quick recovery, and is said to be about 98% recovered.  She is not expected to return to Iraq any time soon.