In the real world, adults who suffer from post-traumatic stress disorder can suffer from a wide range of symptoms: flashbacks to the event (quite rare but which can last anything from a few seconds to several hours or even days, and are dissociative states which are often associated with prolonged distress/heightened arousal), hypervigilancy, seeming easily startled, irritable or having poor concentration.
Particularly, things associated with the traumatic event in question will probably be persistently avoided, and general responsiveness will often seem numbed to some degree. However, the event will probably be re-experienced – in addition to the flashbacks mentioned above, it is not uncommon for there to be recurrent distressing dreams about the event, as well as intense psychological distress at/physiological reactivity to exposure to cues that symbolize or resemble the traumatic event.
Now, as I’m sure you can see from this, I think this would make great roleplay fodder. There are a few caveats here, though.
1) Don’t overdo it. Constantly roleplaying being in the midst of a flashback will probably soon become tiresome to your roleplay partners (unless it becomes comedy gold, of course), and making constant references to hyperviligancy will just get repetitive.
2) Don’t underdo it. Post-Traumatic Stress Disorder isn’t something that effects someone for a little while and is then over with by the next week – it’s a serious psychological disorder and does permeate peoples’ lives. That’s what makes it a disorder and not just being slightly troubled – it will effect their day to day and make their daily routine more difficult. There’s a middle-ground between being annoying and only paying lip-service to the idea, and it can be found with care.
3) Be consistent. If one day they’re confined to their bed at the sight of a troubling item, and the next day they laugh at it as though without a care in the world, there’s something wrong. Sure, people can recover from Post-Traumatic Stress Disorder and make progress and have relapses, but if there’s significant change happening about how they respond over a matter of hours or days, that’s just playing inconsistently. Try to shoot for broadly the same level of responsiveness to the trauma, perhaps gradually changing over time to reflect becoming accustomed to dealing with it, or to reflect slowly growing worse about it.
How can you reflect this in actual play? Well, that depends on a few things – what was the event that troubled them, what will remind them of it, how will they react when they face these things again? If the triggers are combat, for instance, you may be in trouble – will they just stand at the back of the raid group, frozen in fear rather than facing the monster up close? Or is it something they’ll see out of combat and respond to there?
One way that I have considered to get this idea across is with a fire mage. At Level 30, a fire-specced mage can get an ability called Blast Wave, which causes a ring of fire to radiate outward from the caster. If a fire mage is played as suffering from Post-Traumatic Stress Disorder, if they are suddenly startled (which, as I noted before, should be quite frequent), they could let off a Blast Wave to show their startlement. This same trick can be repeated with other AoE’s, but personally I like Blast Wave to really show ‘startlement’ rather than ‘sneezing from cold‘ or ‘really pissed off‘.