It's a layered approach. You approach the acute stress reaction based on simplicity. In the Second World War they called it “three hots and a cot”—you got meals and you got to sleep for a while, which maybe you hadn't done. And as your symptoms subsided over 48 or 72 hours, you went back to work with your unit. They said to keep them within the sound of the guns so they knew they were still on the mission. I'm a firm believer in that.
If that doesn't work, then you end up at Kandahar airfield chatting with the psychiatrist, who may decide it's worth a trial of medication and perhaps some modified duty to keep you in theatre. If that doesn't work, then you will be evacuated out of theatre.
The linchpin of treatment for post-traumatic stress disorder is still cognitive behavioural therapy. It's an anxiety disorder. You have to expose people, in a controlled way, to the thing that makes them anxious and teach them to reprocess it.