The study also found that women with PTSD diagnosis or sub-threshold PTSD had significantly more severe depression symptoms than those who did not report experiencing trauma.
Researchers at Northwestern University in the US examined a disadvantaged Chicago neighbourhood. Every woman who was recruited had symptoms of depression.
"There are many women who are affected by shooting and gang violence in these neighbourhoods. These women are often overlooked," said Sunghyun Hong, research assistant at Northwestern University.
"With this study, we were able to shine a light on this high prevalence of trauma exposure and PTSD diagnosis among the underserved population," said Hong.
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Thirty-six per cent of women in the study had PTSD or sub-threshold PTSD (substantial trauma symptoms that might not have met the full PTSD diagnostic criteria).
Those with PTSD had more severe depression symptoms than other women in the study who did not exhibit signs of PTSD, said Inger Burnett-Zeigler, from Northwestern University.
"Even if you do not meet the full criteria for PTSD, you can have enough symptoms to impact your well-being," Burnett-Zeigler said.
"There is a substantial proportion of people who fall below the PTSD diagnosis line who might be getting lost in the cracks," she said.
A significant percentage of women in a general population who experienced trauma (20 per cent) develop PTSD, she said.
"However, the prevalence of PTSD symptoms is particularly acute in impoverished neighbourhoods. In the study's sample, 71 per cent of the women who experienced trauma had PTSD symptoms," she added.
"This was not a sample we recruited based on having traumatic experiences, and yet so many women we recruited had experienced something traumatic. That is really significant in terms of how prevalent of an issue this is in that vulnerable population," Burnett-Zeigler said.