HEATHROW DIRECTOR,
To put it another way, would you be happy if your wife and kids flew with a pilot who had lied about a medical problem?
Ah, that old chestnut. My answer, in this scenario, would be - "Yes, so long as that pilot was assured in his own mind that he was mentally and physically fit to carry out his or her duties."
PTSD is something no doctor can know about you - only YOU know in your own mind. It is wrong to lie, but if you don't feel you are being deceptive, then fail to mention it at your own risk. I was diagnosed with Asperger's Syndrome aged 8 because I was smarter than all the other kids and was bored, so pi**ed around all the time. Did I mention it on my medical application? Did I hell.