I wrote the following in response to a question on Quora.

Although all of the reasons PTSD develops are not understood, the first thing to keep in mind is that it is a spectrum. For many people it is usually mild and manageable, although it can become quite uncomfortable (or just tiresome) when it is triggered. Realize that hundreds of thousands of public safety workers, who don’t fit any of your categories, live and work with PTSD. Many go though most of their days without giving it a thought.

One of the strong correlations to PTSD risk is how much REM sleep you get. A person who isn’t getting good REM sleep, due to sleep apnea, alcohol or drug use, or anything else that prevents them from dropping into that deeper sleep, is at higher risk. The theory is that our brains consolidate memories during REM sleep, so that we we essentially forget the emotions along with the event. (PTSD is sort of like “remembering” – or re-living – the emotions separately from the event.) There is a good argument that energy drinks and other substances that improve memory also can increase your risk, simply because they improve your memories of the bad event.

It is a mistake to decide if you “should” have a post-traumatic stress injury, based on what happened. “Should” is a word to get rid of in this context. What matters is how you reacted. I meet with people who witnessed or experienced terrible things, but they don’t have a strong reaction – they didn’t feel particularly helpless or out of control. They may not need any intervention at all, even though the incident would have been traumatic for many other people. But the converse is true – a person can experience extreme feelings of helplessness and out-of-control from a seemingly “minor” event and have a significant post-traumatic stress injury. Although those events usually involve loss of life or the threat of it, serious injury, etc. , the common factor is the reaction, not what happened.

There is absolutely nothing in the news article that would indicate whether or not someone involved might be at risk for PTSD. Again, the facts of what happened are not very important; your perception of what happened, along with physiological factors and what else you may have experienced previously (prior trauma can set you up for a more serious injury) all contribute.

I often invite people in your position to say this to themselves: “My stress is the worst stress because it is MY stress.” Comparing yourself to others – especially based only on the facts – is always a mistake (“No comparison stress shopping.”)

Be gentle with yourself. Be as gentle with yourself as you would be with a friend who had the same reactions.

I doubt there is any guaranteed way to become immune to PTSD, but if you aren’t getting good REM sleep and can make changes to do so, that almost certainly will help. Social support has also been shown to correlate to reducing the impact of traumatic events. Connecting with your body and nature – things like meditation, yoga, hiking – also help to activate the part of your nervous system that tells your “fight or flight” response that it is safe to de-activate. Spirituality, in the sense of having bigger-than-self values, also seems to help.

Stress doesn’t have to be toxic. Kelly McGonigal (“The Upside of Stress”) gives a good summary of this in her TED Talk. Watch to the very end, where she gives a great bit of advice: “Chasing meaning is better for your health than trying to avoid discomfort.”