Women who suffer from both depression and post-traumatic stress disorder are at nearly four times the risk of early death from cardiovascular disease, diabetes, suicide and other causes than women who do not, a recent study found, underscoring the impact mental health has on physical health.

The Harvard T.H. Chan School of Public Health study, which was published online in JAMA Network Open on Dec. 4, followed more than 50,000 women for up to nine years. It found that those individuals who had both PTSD and depression had a 3.8-fold increased risk of death during that period of time, compared to those without trauma exposure or depression. The women studied ranged in age from 43 to 64 years, with an average age of about 53.

Andrea Roberts, lead author on the study and a senior research scientist at Harvard’s department of environmental health, said she was “astonished” at the results of the investigation.

“You just don’t see a fourfold increase of things when you study health, almost ever,” Roberts said. “To have a health outcome which is death, which is such a severe health outcome, it’s pretty shocking, and it really points to the extent to which our physical health follows our mental health.”

Previous research into what triggers PTSD has indicated that the more personally severe the trauma is, the higher the chance is of the disorder developing. Roberts said that previously, PTSD was viewed as something that developed subsequent to a severe event, such as a car crash leading to grievous injury or a natural disaster causing large property damage; much of the earlier research into the disorder had also viewed it as being directly related to military service. However, more recent evidence has suggested that relatively milder events, such as a messy divorce, can also lead to the development of PTSD symptoms.

As for the comorbidity examined in this study, Roberts said that while women can develop depression without experiencing a traumatic event, it is more common in those who have experienced trauma, and that such an event can trigger both PTSD and depression. Additionally, there are common overlapping symptoms between both depression and PTSD, such as general feelings of sadness or a lack of joy.

“It’s not completely understood,” Roberts said. “There’s this idea that there’s a kind of synergy between them, like if you develop depressive symptoms you might be more vulnerable to PTSD, and vice versa.”

Given the physical toll that having both PTSD and depression can take, Roberts stressed the importance of effective treatment, which can unfortunately turn into a costly barrier for many people.

“The most effective treatments for depression and PTSD usually involve some sort of one-on-one therapist, which is expensive,” Robert said. “They also often involve pharmaceuticals, which are not expensive, but pharmaceuticals on their own tend to be not that effective. A lot of studies have shown that you get the highest sort of remission of symptoms if you have both therapy and pharmaceuticals together.”

A lack of detection can also be an issue for both PTSD and depression, with both disorders often going undiagnosed due to a lack of appropriate screening at general practitioners, Roberts said, adding that a parallel issue is the social stigma attached to mental health concerns.

“Many people who experience depression or PTSD or other mental health problems, there’s a huge amount of stigma, which is completely unnecessary and historical in origin,” Roberts said. “It prevents people from getting treated.”

The study highlighted the need for a broader awareness not just of PTSD and depression, but of how mental health issues at large can have a severe impact on physical health, Roberts said.

“We’re all aware that stress is not good for us,” Roberts said. “But I don’t think that people, especially the medical community, are as aware of how important our mental health is just in terms of our general health. It’s just really fundamental.”

The study, “Association of Posttraumatic Stress and Depressive Symptoms With Mortality in Women,” was published online in JAMA Network Open on Dec. 4. It was authored by Andrea Roberts, Laura Kubzansky and Lori Chibnik, all of the Harvard T.H. Chan School of Public Health.