What thesis statement can I use for returning soldiers with PTSD?

That depends on your approach to the topic, or if there is a specific question about soldiers with PTSD that you are supposed to address.  As for the topic of PTSD and the soldiers now returning from deployment in Afghanistan and Iraq, a thesis statement could look something like this:

American society is witnessing a rapid rise in the rates of PTSD among returning soldiers from Iraq and Afghanistan due to the type of guerrilla warfare and IED attacks faced by those soldiers, and the frustration and stress they experience by being under constant threat of attack by an elusive enemy practicing hit and run tactics.