Third, judging the relative severity of traumatic events is problematic. An implicit assumption since 1980, when DSM-III was published, has been that the risk of PTSD is uniformly high across the distinct set of stressors bracketed in criterion A. However, the DSM-III text introduced another principle when it noted that ‘Some stressors frequently produce the disorder (e.g. torture) and others produce it only occasionally (e.g. car accident)’ (APA, 1980, p. 236). In other words, etiological stressors are heterogeneous; severity can be surmised from the frequency with which they cause PTSD, their pathogenicity (Tolin & Foa, 2006). This is the approach we take here when we define sexual assault as a severe trauma, relative to accidents, disaster and sudden unexpected death of someone close. Notably, this is the strategy adopted by the DSM-5 committee responsible for revising PTSD toward the goal of improving diagnostic validity. The committee has sought evidence on the potency of specific event types to cause PTSD in order ‘to make a better distinction between traumatic and events that are distressing but which do not exceed the “traumatic” threshold’ (APA, 2011).
