The percentage of post-9/11 veterans who feel their transition to civilian life has been difficult, according to a Pew Research Center study -- War and Sacrifice in the Post-9/11 Era: The Military-Civilian Gap (October 2011). According to the report, just 25% of the veterans who served in earlier eras feel the same way.
Furthermore, the Pew study found:
Nearly four-in-ten (37%) post-9/11 veterans say that, whether or not they were formally diagnosed, they believe they have suffered from post-traumatic stress (PTS). Among veterans who served prior to 9/11, just 16% say the same.
Another Pew study -- Women in the U.S. Military: Growing Share, Distinctive Profile (December 2011) -- found that women were less likely to have served in combat than men (30% vs. 57% of men), more likely to have never been deployed from their permanent duty station (30% vs. 12%), and less likely to have served with someone killed in the line of duty (35% vs. 50%).
Nevertheless, according to the report, "... they are equally likely to have had emotionally traumatic or distressing experiences while serving (47% vs. 42% of men), and their transition back into civilian life has been equally tough. More than four-in-ten female post-9/11 veterans (43%) say their readjustment to civilian life after their military service was very or somewhat difficult (along with 45% of men)."