You need to advise the DVLA if your PTSD might affect your driving - your doctor can tell you if that's likely to be the case. If it is, the legal, responsible thing is to tell them and not drive.
I couldn't drive for a number of years due to seizures caused by post traumatic stress - it was a pain, but killing or injuring someone by driving when I wasn't fit would have been much worse.
What does your doctor say about you driving?