Oct 29 (Reuters) - Signs of post-traumatic stress disorder (PTSD) seen in frontline healthcare workers during the COVID-19 pandemic may be linked to trauma that occurred earlier in their lives, according to a study from Oxford University. About three-fourth of the 103 healthcare workers assessed reported a trauma that was unrelated to their work during the pandemic, according to the study published on Friday. "In the 76% of staff who had PTSD that was unrelated to the pandemic, it is likely that the stressful nature of working during the pandemic exacerbated symptoms or made it harder to recover from them," said clinical psychologist Jennifer Wild, who led the study. "There was a significant minority, 24%, who did develop PTSD due to COVID-19 trauma," she added. Nearly 40% of those assessed showed signs of PTSD and depression. The study also noted that major depressive disorder was more likely to develop during the pandemic. While PTSD is associated with combat, it can arise among civilians after natural disasters, abuse or other trauma. Health workers can be reluctant to equate their experience with that of returning soldiers.