PTSD is only a recently studied phenomenon. Even during WWI it was only ever really known as shell shock and not much was really done about it. It was mainly after the Vietnam war that serious study into PTSD was undertaken

But research has shown that PTSD in soldiers has likely existed in every conflict through human history. Which makes sense - although the nature of war has changed it's always been a brutal and traumatic experience

http://www.newhistorian.com/ptsd-found-ancient-warriors/2835/

I've just finished writing my dissertation on this exact topic and, in short, yes. For an in depth study I'd recommend Dr Jonathan Shays 1994 work 'Achilles in Vietnam'. He's a psychiatrist who worked with Vietnam vets and saw they're experiences mirrored in the life of Achilles in the iliad .

There's also an article called 'caesar in Vietnam ' which is excellent, although I've forgotten the author. But in general I think yes, they did suffer from ptsd, there's evidence throughout the primary literature to suggest it which I could past some of later, I'm on mobile at the minute.