According to researchers from the Walter Reed Army Institute of Research there is a connection between concussion experienced on the battlefield and developing Post Traumatic Stress Disorder. Here is a quote from the article:

Among those who experienced loss of consciousness, 44% met criteria for PTSD, compared with 27% of those experiencing altered mental status, 16% with other injuries, and 9% with no injuries. Those who experienced mild traumatic brain injury, particularly if it was associated with loss of consciousness, reported poorer physical health, with more missed work days, medical visits, and somatic and postconcussive symptoms.

Since I am one of those people who briefly lost consciousness and then developed PTSD, I would be within the 44%. However, I think a better study would be comparing the rate for PTSD among servicemen and women who were injured versus those going uninjured physically. For those being injured, I would think there would be a strong correlation. Then again, I am not a scientist.

Feel free to forward me other studies or article you think merit the attention of the public.