Findings should be weighed in light of the study’s limitations. Findings were based on an Internet survey. The fact that the study did not include a true national probability sample of U.S. adults is a limitation, as is the fact that approximately 20% of U.S. adults without Internet access were excluded from the sampling frame. However, the use of a sample drawn from a geographically and demographically diverse national online panel and the application of weighting to the U.S. adult population based on age, sex, race, and ethnicity does offset this limitation and provides some ability to generalize findings to the population of U.S. adults. Also, the comparisons of PTSD prevalence based on the DSM-IV criteria versus the DSM-5 criteria were not affected by any discrepancies between our sample and a true national probability sample. The study did not include a clinician-administered assessment of PTSD, which many view as the gold standard for PTSD assessment, but clinician interviews are impractical and not the norm for large-scale epidemiologic studies. The use of a highly structured self-administered survey measuring traumatic event exposure
