Timothy S. Wells of the U.S. Air Force Research Laboratory, Wright-Patterson Air Force Base in Ohio has been studying more than 40,000 U.S.A.F. personnel who served between 2000 and 2006. They found that among those who experienced combat in Iraq and Afghanistan 6% of men and 16% of women developed depression. In those who were deployed to the two countries but who did not fight the figures were 4% and 8% respectively and in people who did not face combat the figures were 2% and 5%. Male 'combat specialists' had a lower risk for depression than those in health care or other supportive positions while men and women who already had post-traumatic stress disorder (PTSD) were also more likely to develop depressive symptoms. Other risk factors for depression included younger age, smoking and alcohol dependence.
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