According to a new study, gene differences may explain why some people recover from a traumatic event while others develop post-traumatic stress syndrome (PTSD). Researchers looked at 900 adults who suffered abuse when they were children and found that trauma at a young age may cause specific variations in a stress-related gene, and these variations increase the risk of PTSD in adulthood. Among adults who suffered severe child abuse, those with the gene variations scored 31 on a scale of PTSD, compared to 13 for those without the variations.