In DSM-IV, a PTSD diagnosis required that an individual must experience symptoms related to trauma for at least a month in order to meet the diagnostic threshold. Prior to this month, individuals could develop acute stress disorder (ASD) if they experienced similar symptoms to PTSD from 2 days to 4 weeks immediately following the traumatic event. This has been known as “combat operational stress reaction” (COSR) in military circles. The ASD/COSR diagnoses consist of similar symptomatology to PTSD, with some salient differences. Whereas in PTSD, no dissociative symptoms were necessary to meet diagnostic criteria, in ASD, an individual must have displayed three dissociative symptoms (APA, 2000). Examples included a reduced awareness, such as being in a daze or daydream (Criterion B2), derealization or feeling that the external world is strange or somehow unfamiliar (Criterion B3), depersonalization or feeling detached from oneself as if in a dream or an out-of-body experience (Criterion B4), and dissociative amnesia or unable to remember important information about the traumatic event (Criterion B5). In ASD, symptoms must only be present for the first month. If these symptoms persisted for longer than 1 month, an individual qualified for a diagnosis of PTSD.

Significantly, 70–80 % of individuals with ASD/COSR eventually developed PTSD, yet 60 % of individuals with a PTSD diagnosis did not meet the diagnostic criteria for ASD (Classen, Koopman, Hales, & Spiegel, 1998). This lack of consistency between PTSD and ASD has led for calls to abandon the ASD diagnosis, and replace it instead with a V-code entitled “acute stress reaction” (Spitzer et al., 2007). This would be harmonious with empirical knowledge that fully functioning (i.e., “normal”) individuals often seek professional help after exposure to a stressor/trauma, though do not exhibit psychopathology (McHugh & Treisman, 2007). Changing ASD/COSR to a V-code could be considered a step toward reducing the stigma of help-seeking behavior following exposure to a stressor or traumatic event, but the change would also have implications for reimbursement for treatment.

During the planning phase for the DSM-5, many argued that PTSD should be considered a part of another diagnostic category (Miller, Resick, & Keane, 2009), rather than classified as an anxiety disorder. Proponents maintained that a separate category was warranted because the dysphoric symptoms of PTSD appeared to be more consistent with non-anxiety disorders, such a major depressive disorder and dysthymia, rather than fearful anxieties, such as phobias (Resick & Miller, 2009). Furthermore, PTSD could be conceptualized as a unique diagnostic condition, due to the necessary presence of an identifiable cause (i.e., “traumatic event”) in order for a diagnosis to be made. Miller et al. (2009) proposed a distinct category for these types of disorders, which included PTSD, acute stress reaction, adjustment disorder, traumatic grief, and possibly complex PTSD. Yet another proposed change was to delineate heterogeneous classifications of posttraumatic disorders, such as “posttraumatic dental care anxiety,” “posttraumatic grief disorder,” “posttraumatic abortion syndrome,” and “posttraumatic embitterment syndrome” (Coyne & Thompson, 2007; Rosen & Taylor, 2007). Research into the relationship between mild traumatic brain injury and PTSD resulting from military combat in the recent U.S.-Iraq war led to the proposed category of “combat-related mild-traumatic brain injury” (Hoge et al., 2008). In response to these arguments, the APA decided to include PTSD in a new chapter in the DSM-5 on Trauma- and Stressor-Related Disorders, which also includes reactive attachment disorder, disinhibited social engagement disorder, acute stress disorder, and adjustment disorders.

All primary diagnostic criteria identified by the DSM-IV for PTSD were examined for possible revisions, and the approved DSM-5 diagnostic criteria (APA, 2012, 2013) for PTSD included a number of significant restrictions to Criterion A1 that tightened the operational definition of exposure to a traumatic stressor. First, witnessing an event no longer qualified, unless the person was physically present. Observing an event through the media (e.g., television, radio, Internet) was excluded, unless such mediated exposure was related to work (e.g., law enforcement), and involved repeated or extreme exposure. The second restriction was that learning about a loved one’s trauma only qualified as exposure if the incident had involved an actual or threatened death by violence or accident. These revisions were in response to a vigorous debate among various scholars (e.g., Brewin, Lanius, Novac, Schnyder, & Galea, 2009; Friedman, Resick, Bryant, & Brewin, 2011; Long & Elhai, 2009; Spitzer et al., 2007).

Another major change in the DSM-5 was the elimination of Criterion A2, which required an intense emotional reaction to the event, because it had been demonstrated that it lacked predictive utility (Bovin & Marx, 2011). Moreover, as McNally (2009) argued, this elimination brought greater conceptual clarity to Criterion A by focusing only on the external stimulus, rather than including the person’s internal responses, which were covered more precisely in the other symptom clusters.

Minor revisions have been made in Criterion B specifying that nightmare content must be trauma-related, and clarifying that flashback episodes were dissociative reactions. The most prominent change in the symptom clusters involved highlighting the distinctions between avoidance and emotional numbing. Since the DSM-III, these symptoms have been combined in Criterion C. However, the new revision divided these into two separate symptom clusters because research had demonstrated that avoidance and numbing are distinct and separate factors (Asmundson, Stapleton, & Taylor, 2004; Elhai & Palmieri, 2011). The new Criterion C included two avoidance symptoms involving internal and external reminders of the traumatic event. Research in different countries had suggested that avoidance/numbing symptoms (Criterion C) have more predictive validity for a PTSD diagnosis than persistent re-experiencing of an event (Criteria B) or hyperarousal (Criterion D; North, Suris, Davis, & Smith, 2009). In addition to including psychic numbing, Criterion D of the DSM-5 added new depressive symptoms. These included self-blame, pervasive negative emotions, and persistent negative perceptions of oneself, others, or the world (Contractor et al., 2013). Criterion E is an elaboration of the arousal symptom cluster that appeared in previous editions of the DSM. In addition to sleep disturbances, hypervigilance, and exaggerated startle response, it added reckless or self-destructive behavior, irritability, and aggressive behavior. Finally, DSM-5 enabled specification of delayed expression of PTSD, even if some of the symptoms occurred up to 6 months after the event. As noted earlier, some studies have indicated that delayed onset of PTSD occurs very rarely (Andrews, Brewin, Philpott, & Stewart, 2007; Frueh, Grubaugh, Yeager, & Magruder, 2009).

These changes in PTSD in the DSM-5 are considered by some to be minor improvements over the DSM-IV criteria (Frueh, Elhai, & Acierno, 2010). Although they may contribute to conceptual clarity, the changes are not likely to affect the prevalence of PTSD diagnoses (Elhai et al., 2012). Recent studies, using these PTSD criteria, have found that 89 % of veterans meeting the DSM-IV diagnostic threshold for PTSD also met the new DSM-5 diagnostic threshold for PTSD (Miller, Chard, Schumm, & O’Brien, 2011). However, given the increase in the number of diagnostic criteria for PTSD in the DSM-5, Galatzer-Levy and Bryant (2013) calculated that 636,120 different combinations of symptoms could fulfill the diagnosis. They argued that such heterogeneity is a consequence of the DSM’s checklist approach and threatens to sabotage the reliability and validity of the diagnosis of PTSD.

In an attempt to be more developmentally sensitive, a separate list of diagnostic criteria for children 6 years or younger is provided in the DSM-5. The major difference from the criteria for those older than 6 years, other than minor changes in wording, is that negative alterations in cognitions are not separated into a new major category. A proposal to include a new diagnosis, Developmental Trauma Disorder (DTD), was forwarded for inclusion in DSM-5 (Moran, 2007; van der Kolk & Pynoos, 2009). This diagnosis was proposed based upon findings from developmental psychopathology, clinical presentations of children and youth exposed to chronic interpersonal violence, and emerging evidence from the field of neurobiology regarding the impact of trauma on brain development. Proponents noted that the DSM’s PTSD criteria did not capture clinically relevant symptoms for children living in chronically unsafe conditions. The supporters of DTD acknowledged the relevance of the PTSD diagnosis for a child experiencing a single incident trauma and living in a secure caregiving relationship. However, they argued, the practical impact of the PTSD criteria for DSM-5 is harmful for children who undergo multiple and complex traumas, especially for children exposed to harmful caregiving. The supporters contended that the criteria may result in no diagnoses, inadequate diagnoses, or inaccurate diagnoses for these children (van der Kolk & Pynoos, 2009). The proposal for DTD was not accepted for inclusion in DSM-5, but the discussion of the merits of an alternative classification system for children experiencing complex trauma is continuing.

Importantly, DSM-5 includes the first developmental subtype of a disorder: Posttraumatic Stress Disorder in Preschool children. Studies that compared the use of developmentally sensitive criteria resulted in approximately three to eight times more children qualifying for diagnosis compared to the use of DSM-IV (Scheeringa, Myers, Putnam, & Zeanah, 2012; Scheeringa, Zeanah, & Cohen, 2011). These findings support need for age-related criteria, given the cognitive and verbal capacities of preschool age children. Some symptoms were deleted and the wording was modified on others to be more behaviorally based, for example, “Diminished interest in significant activities may manifest as constriction of play.” Preliminary evidence supports the criterion, discriminant, and predictive validities of the preschool PTSD criteria (Scheeringa et al., 2011).