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According to the researchers, one in nine women will have post-traumatic stress disorder (PTSD) at some point in her life. That's twice as often as men. Women are more likely to experience traumatic events, such as rape, which carry a high risk for PTSD, the study authors said.
"PTSD is not just about mental health, but also has physical health consequences," said lead researcher Karestan Koenen, an associate professor of epidemiology at Columbia University's Mailman School of Public Health, in New York City.
Women with PTSD gain weight faster than women who do not have the condition, Koenen said. "This, in turn, has consequences for the risk of heart disease and all the adverse outcomes associated with obesity," she said.
PTSD linked to weight gain
How PTSD is linked to weight gain isn't known, Koenen said, but it may be caused by the high levels of hormones released because of stress.
These hormones are involved in a range of body processes, including metabolism, she said.
"In addition, women with PTSD may change behaviours that lead to obesity," Koenen said. "There is evidence that people under stress crave high-calorie processed foods, so it could be diet." These women also are less likely to exercise, she said.
Koenen said the same problem may exist in men suffering from PTSD, but this hasn't been well studied.
The new report was published in the online edition of the journal JAMA Psychiatry.
For their research, Koenen and her colleagues collected data on more than 50 000 women who took part in the Nurses' Health Study II between 1989 and 2009. Their ages ranged from 22 to 44 at the study's start.
The women were asked about the worst trauma they experienced and if they had symptoms of PTSD. Symptoms included re-experiencing the traumatic event, feeling threatened, avoiding social situations and feeling emotionally numb. PTSD was defined as having four or more symptoms over a month or more.
Other factors in weight gain
The researchers found that women originally of normal weight who developed PTSD had a 36% higher risk of becoming overweight or obese, compared to women who, despite experiencing trauma, didn't develop PTSD.
This finding held even after taking into account other factors, such as depression, that have also been considered major factors in weight gain, the researchers said.
In women who had PTSD before the study period began, weight increased more rapidly than it did among women without PTSD.
Although the study found an association between women having PTSD and a higher risk for obesity, it did not establish a cause-and-effect.
Impact on physical health
"This important study highlights, once again, the significant impact that psychological disorders can have on physical health," said Simon Rego, director of psychology training at the Montefiore Medical Centre and Albert Einstein College of Medicine, in New York City. He was not involved with the research.
Rego said trauma and obesity are both common in today's society. They can cause distress, difficulty in functioning and disability, he said, and all these conditions are hard to treat. That's why it's important for doctors to understand the impact of PTSD symptoms -- not only on mental health, but also on physical health.
Treating PTSD might also help in reversing weight gain, he said. "Doctors... should be encouraged to screen for PTSD, especially in populations at high risk for trauma but also in patients presenting with obesity," he said.
If PTSD symptoms are found, the patient should be referred to a clinical psychologist or other mental-health professional with expertise in treating PTSD, Rego said.
More information
To learn more about post-traumatic stress disorder, visit the US National Institute of Mental Health.
