The study was one of the first to use prospective methods of study to look at the relationship between PTSD and prior psychiatric status, meaning the researchers collected data while following groups of soldiers over a period of time rather than simply collecting data about events in the past.
The results showed that soldiers who already had signs of PTSD prior to deployment were five times as likely to develop the disorder post-deployment, while those who had a different mental health issue prior to deployment were 2.5 times more likely to develop PTSD. The researchers also found that injury severity among those who were injured during deployment was also related to likelihood of developing PTSD, with a 16.1% greater chance of PTSD for every three-unit increase on the Injury Severity Score.
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According to the researchers, evaluation of pre-deployment mental health "might be useful to identify a combination of characteristics of deployed military personnel that could predict those most vulnerable or, conversely, those most resilient to post-deployment PTSD, thereby providing an opportunity for the development of pre-deployment interventions that may mitigate post-deployment mental health morbidity."