It is thought that between 40-70% of Americans have experienced traumatic events yet only about 8% go on to develop post-traumatic stress disorder (PTSD) over the course of their lifetimes. Researchers from Yale University studied 1,252 people aged from 17 to 79 who had experienced adversity in their childhood and/or as an adult. People who had experienced adverse events in both adulthood and childhood were much more likely (29%) to develop PTSD than people who had 'only' experienced adversity in one part of their life (9.9%). A gene called 5-HTTLPR was also found to influence whether people developed PTSD or not but it was only found to increase in people who had had a double dose (in childhood and as an adult) of trauma.
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