The U.S. Department of Veteran Affairs estimates that around eight million adults in the United States experience post-traumatic stress disorder (PTSD) in a given year. Women experience PTSD at a much greater rate than men. Estimates from the USDVA indicate that 10 percent of women and 4 percent of men are affected by PTSD. Instances of PTSD are similarly prevalent in Canada, where the Canadian Psychological Association estimates that around 8 percent of Canadians who experience a traumatic event develop PTSD. Though no one is immune to PTSD, rates of the disorder among combat veterans are significantly higher than the rates among the general population. USDVA reports that one study of 1,938 veterans found that the prevalence rate among Gulf War veterans was around 14 percent, while an older study from the American Psychological Association found that about 30 percent of Vietnam War veterans had PTSD in their lifetime.