According to RAND, at least 20% of Iraq and Afghanistan veterans have PTSD and/or Depression, although it is believed to be higher due to under-reporting.
Other accepted studies have found a PTSD prevalence of 14%; see a complete review of PTSD prevalence studies, which quotes studies with findings ranging from 4 -17% of Iraq War veterans with post-traumatic stress disorder).
A comprehensive analysis, published in 2014, found that for PTSD: “Among male and female soldiers aged 18 years or older returning from Iraq and Afghanistan, rates range from 9% shortly after returning from deployment to 31% a year after deployment. A review of 29 studies that evaluated rates of PTSD in those who served in Iraq and Afghanistan found prevalence rates of adult men and women previously deployed ranging from 5% to 20% for those who do not seek treatment, and around 50% for those who do seek treatment. Vietnam veterans also report high lifetime rates of PTSD ranging from 10% to 31%. PTSD is the third most prevalent psychiatric diagnosis among veterans using the Veterans Affairs (VA) hospitals.”PTSD and comorbid AUD”, Subst Abuse Rehabil. 2014; 5: 25–36, Ralevski, et al.