Second, NESARC, like other epidemiological studies of its kind, measured PTSD in reference to one traumatic event. A majority of community residents report multiple events; a complete assessment of PTSD for each event would impose too heavy a respondent burden. The standard shortcut for respondents reporting multiple events is to ask the respondent to single out the worst event out of the list of traumatic events they had experienced. This approach was applied in NESARC. The worst event method identifies nearly all PTSD cases (Breslau et al. 1997). A study that compared the PTSD risk based on the worst events with the PTSD risk based on a representative sample of events, selected randomly from the pool of traumatic events reported by each respondent, revealed only minor differences in the PTSD risk within the same event type Breslau et al. 2004). Clearly, information on the PTSD effects of all traumatic events would be preferred over a shortcut. However, the standard shortcut introduces little bias in evaluating the conditional probability of PTSD across individual event types, according to the empirical evidence. [The
