As noted in Chap. 1, people at risk for PTSD have not only been exposed to a severely stressful event but must also exhibit a pattern of symptoms embedded within four symptom “clusters”: intrusion, avoidance, negative mood and cognitions, and arousal and reactivity—as well as meeting the duration and functional impairment criteria.

Before reviewing the DSM-5 symptoms of PTSD in depth, here is a brief introduction.

Figure 2.1 on page XX provides an overview of these symptom clusters.

When first introduced in 1980 in the DSM-III [1] and later in the 1994 DSM-IV [2], PTSD was classified as an anxiety disorder for two reasons. First, altered arousal and reactivity symptoms such as insomnia, irritability, and difficulty concentrating (see below) are found in other anxiety disorders such as panic disorder and generalized anxiety disorder. Second, animal models, such as inescapable stress and fear conditioning, have long been understood within an anxiety context [3]. However, more recent research has shown that for many patients with PTSD, the fear-based anxiety symptoms are not the most prominent and are not the symptoms that require the most clinical attention. For example, for some PTSD patients, the major problem is the negative alteration in mood and cognitions (as also seen with depression), expressed as anhedonia or dysphoria. For others, hyperarousal and reactive behaviors such as angry outbursts or reckless/risk-taking behaviors predominate. Others exhibit dissociative symptoms that are very disruptive. And most exhibit mixed clinical pictures characterized by different combinations of the aforementioned phenotypes [4, 5]. For these reasons, PTSD was removed from the anxiety disorder cluster in DSM-5 and reclassified as a Trauma and Stressor–Related Disorder. This category also includes acute stress disorder (ASD), adjustment disorders, and two child diagnoses, reactive attachment disorder and disinhibited social engagement disorder. All diagnoses in the trauma and stressor-related disorder clusters have in common (as a diagnostic criterion) that their onset was preceded by exposure to a very aversive event. In the case of PTSD and ASD, such events must have been traumatic. For the others, the event need not have been traumatic, but must have been aversive (such as rejection, failure, bankruptcy, or parental maltreatment).

To be diagnosed with PTSD, a person must have been exposed to trauma and experienced symptoms for at least a month after exposure. Figure 2.2, on page xx, presents the Diagnostic and Statistical Manuel, fifth edition: DSM-5 criteria for PTSD (pages 271–274).

People who meet the DSM-5 A criterion have been exposed to catastrophic events that involve actual or threatened death, serious injury (e.g., military combat, sexual assault, physical attack, torture, man-made/natural disasters, accidents, incarceration, or exposure to war zone/urban/domestic violence ), or sexual violence (criterion A1). Others meeting the A criterion include people not directly endangered but who witness such events (criterion A2) and people who witness the violent aftermath of a catastrophic event (such as dead body parts) but were never personally in danger (criterion A4). Finally, DSM–5 includes people who have learned that a loved one was exposed to a life-threatening event or sexual violence but were never in any personal danger themselves (criterion A3). If a loved one died during such an event, the death must have been violent or accidental in order to meet criterion A3.

Children, especially those aged 6 years and younger, who lack an adult’s capacity for abstract thinking or linguistic expression, may express their PTSD symptoms behaviorally rather than verbally through developmentally appropriate, nonverbal indicators of psychological distress, such as disorganized or agitated behavior during play. Because a number of PTSD symptoms require introspective sensitivity and cognitive capabilities that are not present in younger children, the DSM-IV prevalence of PTSD among preschool children has been much lower than for older age groups [6]. As a result, a special preschool subtype has been included in DSM-5 that eliminates subjective symptoms and lowers the number of symptoms to meet the full PTSD criteria. As shown in Fig. 2.2, these changes primarily affect criteria C and D. Instead of needing to fulfill both C and D criteria, preschool children only need to exhibit 1 symptom from either criterion C or D. Furthermore, elimination of subjective symptoms has left only 4, rather than 7 (adult), symptoms in criterion D. Finally, adult criterion E2 has been eliminated since it is difficult to identify “reckless” behavior in children 6 years and younger. These changes are based on strong empirical evidence that PTSD symptoms and symptom thresholds are appropriate for this age group.