may be present. 
Prevalence
In the United States, projected lifetime risk for PTSD using DS M-IV criteria at age 75 years
is 8.7%. Twelve-month prevalence among U.S. adults is about 3.5%. Lower estimates are
seen in Europe and most Asian, African, an d Latin American countries, clustering around
0.5%–1.0%. Although different groups have di fferent levels of exposure to traumatic
events, the conditional probability of developi ng PTSD following a similar level of expo-
sure may also vary across cultural groups. Rates of PTSD are higher among veterans and
others whose vocation increases the risk of tr aumatic exposure (e.g., police, firefighters,
emergency medical personnel). Highest rates (r anging from one-third to more than one-
half of those exposed) are found among surv ivors of rape, military combat and captivity,
and ethnically or politically motivated intern ment and genocide. The prevalence of PTSD
may vary across development; children and adolescents, including preschool children,
generally have displayed lower prevalence following exposure to serious traumatic
events; however, this may be because previo us criteria were insufficiently developmen-
tally informed. The prevalence of full-thresh old PTSD also appears to be lower among
older adults compared with the general popu lation; there is eviden ce that subthreshold
presentations are more common th an full PTSD in later life and that these symptoms are
associated with substantial clinical impairme nt. Compared with U.S. non-Latino whites,
higher rates of PTSD have been reported among U.S. Latinos, African Americans, and
American Indians, and lower rates have been reported among Asian Americans, after ad-
justment for traumatic exposu re and demographic variables.
Development and Course