LotR -- Book 1 - Chapter 12 - Flight to the Ford

[Lalwendë]

Clearly he begins to suffer from post traumatic stress

Davem - this is something I really agree with. After I was diagnosed with PTSD (post traumatic stress disorder) myself I viewed Frodo's sufferings in a whole new light. One of the aspects most clearly demonstrated is his pain on the anniversary of the attack, an anguish which cannot be cured, and which Frodo is unable to cope with. There is also Frodo's inability to accept the truth of what happened, that he was attacked and was not responsible; there was nothing he could do about an unexpected stabbing. He also acts out of character at stressful times - the best example being his refusal to give up the ring at Mount Doom.

Frodo's first reaction, that he may be maimed for life, rings a bell with me - it is the immediate sense of fear and regret. He then has nightmares, and imagines that Aragorn is one of the ringwaraiths; he is seeing the potential for trauma in other, harmless things. After his physical recovery, the trauma still remains to be brought to the surface under stressful circumstances, in situations which remind him of the attack, and on anniversaries.

As davem says, hobbits are not a warlike people and would never expect to be injured by a sword in an unprovoked attack, so this life event naturally takes a devastating toll on Frodo. Although I don't think PTSD was recognised until relatively recently (correct me if I am wrong), it is said that the widespread shell-shock of WWI was basically PTSD, and I don't doubt that seeing the effect that this had was translated into Tolkien's own writing when he wished to decribe the effects of the attack on Frodo.