34: Trauma and Posttraumatic Stress Disorder

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CHAPTER 34 Trauma and Posttraumatic Stress Disorder


The psychopathological impact of exposure to traumatic events has long been recognized, particularly in the context of war. Descriptions of the emotional sequelae of combat date back thousands of years as revealed, for example, in the epic account of Achilles in Homer’s Iliad. Modern wars have engendered their own unique labels for these sequelae, for example, “nostalgia” or “soldier’s heart” (Civil War), “shell shock” (World War I), “battle fatigue” or “combat neurosis” (World War II), and “delayed stress” (Vietnam War). However, stress disorders were largely ignored as a formal psychiatric nosological category and were relegated to “transient” phenomena until the publication of the Diagnostic and Statistical Manual of Mental Disorders, Third Edition (DSM-III) in 1980. Consistent with this history, the inclusion of posttraumatic stress disorder (PTSD) in the DSM-III appeared largely in response to the psychiatric difficulties experienced by war veterans, in this case, soldiers returning from Vietnam. As a result, much of the original work underlying the diagnosis of PTSD focused on combat veterans. Since that time, however, the conceptual and empirical basis of PTSD has broadened significantly to include obvious sources of civilian trauma (including, but not limited to, assaults, childhood abuse, natural disasters, and accidents). Indeed, the most recent editions of the DSM now recognize witnessing death or the injury of others, or even learning about the unexpected death of a friend or family member, as traumatic events that can be conceptualized within the framework of PTSD. Because the diagnosis of PTSD is frequently associated with trauma that occurs within strong social (e.g., rape or child abuse), political (e.g., war), or legal (e.g., tort civil litigation) contexts, it has frequently engendered controversy; the diagnosis has even been considered by some to reflect a mere “social construction” or a form of “victim advocacy.” However, more than two decades of epidemiological, genetic, and biological research has firmly established an empirical foundation for PTSD. It is now recognized as a major psychiatric condition with significant social and occupational impact.



The diagnosis of PTSD is unique among psychiatric disorders in that the diagnostic criteria contain the presence of a presumptive etiology (i.e., a traumatic event), in addition to the more typical symptom constellation (Table 34-1). The current DSM-IV criteria require that the traumatic event (criterion A) be defined by two elements: the individual must have experienced, witnessed, or learned about an event that involved actual or threatened death or serious injury (A1); and the individual’s response to this experience must involve intense fear, helplessness, or horror (A2).

Table 34-1 DSM-IV Diagnostic Criteria for Posttraumatic Stress Disorder (309.81)

Specify if: Acute: If duration of symptoms is less than 3 months Chronic: if duration of symptoms is 3 months or more Specify if: With delayed onset: if onset of symptoms is at least 6 months after the stressor

As previously noted, the DSM-IV stressor criterion significantly broadens the concept of a traumatic stressor from earlier versions of the DSM (that had conceptualized trauma as involving an event that is “outside the range of usual human experience”) (DSM-III-R). Thus, more common experiences (such as learning about an unexpected death or injury of a friend or family member) can be conceptualized as trauma by DSM-IV standards. The DSM-IV change in stressor definition (i.e., A1) may have increased the number of stressors that qualify for inclusion by nearly 60%.1 The addition of the A2 subjective element of the stressor (e.g., the presence of intense fear, helplessness, or horror) has likely had only a modest impact, given that more than three-quarters of individuals exposed to trauma endorse this response (90% of those who fully meet PTSD symptom criteria B, C, and D report also experiencing the A2 subjective element at the time of traumatic exposure).1,2 The net effect of combining the more inclusive nature of the DSM-IV A1 criterion with the modestly limiting A2 criterion has been to produce an increase of over 20% in the total number of qualifying traumatic events compared to earlier versions of the DSM.

Clinical Features

The symptomatology of PTSD is conceptualized within the framework of three symptom clusters (see Table 34-1): reexperiencing (criterion B; one of a list of five symptoms is required), avoidance (criterion C; three of a list of seven symptoms are required), and arousal (criterion D; two of a list of five symptoms are required). Factor analytic studies have supported this symptom structure for PTSD. However, most studies have suggested that the avoidance cluster represents two independent factors: avoidance (criteria C1 to C3) and numbing (criteria C4 to C7), the latter being associated with a more pervasive disturbance.3,4 The most common symptoms reported by individuals in the aftermath of trauma include sleep disturbance, intrusive memories/nightmares, and avoidance of reminders. For trauma-exposed people, the re-experiencing criterion B is most frequently met (reported in 60% to 80% of trauma survivors), followed by the arousal criterion D (seen in 30% to 60% of people).5,6 The avoidance/numbing criterion C is the least frequently observed (10% to 50%) among trauma-exposed individuals.5,6 Thus, it is a critical determinant of PTSD. In a study of survivors of the Oklahoma City bombing, only one-third of exposed individuals met the avoidance/numbing criterion (compared with more than 80% who met re-experiencing and arousal criteria).7 Of those who endorsed avoidance/numbing, there was a 94% probability of eventually meeting the criteria for PTSD. Trauma-exposed men are generally less likely than are women to meet the avoidance/numbing criterion. Even among victims of assault, only 20% of men meet criterion C compared with 50% of women.5

Many individuals fail to meet criteria for PTSD due to a failure to meet criterion C (avoidance/numbing). The prevalence of “subthreshold” or “partial” PTSD (often defined as meeting two of the three symptom clusters and having at least one symptom from the third) is believed to be two to four times more common than is full PTSD.8 Moreover, individuals with subthreshold PTSD demonstrate considerable occupational and social impairment relative to trauma-exposed controls; in some cases they demonstrate impairment comparable to those with PTSD.9 Furthermore, subthreshold PTSD is more closely linked with suicidal ideation (comparable to full PTSD) even after controlling for the presence of depression.10

Acute Stress Disorder

The DSM-IV introduced a new diagnostic category, acute stress disorder (ASD), to recognize brief stress reactions to traumatic events that are manifest in the first month following a trauma. Criteria for ASD appear in Table 34-2. In addition to a shorter duration (2 days to 4 weeks), ASD has a less restrictive set of PTSD symptoms in each of the three cluster types (re-experiencing, avoidance, and arousal) plus the requirement of meeting 3 out of 5 dissociative symptoms. Derived from theory, ASD represents one of the few disorders in the DSM-IV without prior empirical validation. As a result, controversy exists as to whether the diagnostic criteria for ASD constitute an optimal or meaningful clinical picture for those who experience acute stress in the aftermath of trauma. In particular, its emphasis on dissociative symptoms has been questioned.

Table 34-2 DSM-IV Diagnostic Criteria for Acute Stress Disorder (308.3)

Empirical studies have suggested that the ASD symptom cluster occurs in 10% to 30% of individuals exposed to trauma.11 Prospective studies suggest that 72% to 83% of those diagnosed with ASD go on to develop PTSD at 6 months after the trauma, and 63% to 80% have PTSD at 2 years after the trauma.11 Although dissociation in the acute posttrauma phase has led to significant predictive power for PTSD, its role within ASD may nonetheless be overemphasized. When the dissociation criterion is removed from the ASD diagnosis, comparable rates of subsequent PTSD are observed, that is, 60% of patients with ASD (minus dissociation) are reported to have PTSD 6 months after the trauma, and 70% report symptoms of PTSD 2 years after the trauma.12,13 In a similar vein, the application of the standard PTSD diagnostic criteria, without the 1-month duration, in the first month following trauma has been as effective as the ASD diagnosis in predicting subsequent and persistent PTSD.14,15 Regardless, the clinical utility of the ASD diagnosis has been supported by studies that have examined early treatment in such individuals. Preliminary research has suggested that the employment of specific treatment approaches (e.g., exposure therapy, cognitive therapy, stress management) for ASD leads to lower rates of later PTSD (approximately 15% to 25% at 6 months after the trauma) relative to ASD patients who are either untreated or who receive general supportive counseling (approximately 60% to 70% have PTSD at 6 months).11 Despite evidence regarding the prevalence and utility of the diagnosis of ASD, unresolved issues remain, not only with regard to its emphasis on dissociative symptoms, but also as to whether ASD and PTSD may in fact represent the same disorder, the latter merely differentiated by an arbitrary month-long duration criterion. In other words, ASD may simply exemplify “acute PTSD” as defined in the earlier DSM-III.15



While the lifetime prevalence of PTSD in the general community is 8% to 9%, the 12-month prevalence of PTSD is nearly 4% (with more than two-thirds of cases manifest by moderate to severe functional impairment).1618 Women show a higher lifetime prevalence (10% to 14%) than do men (5% to 6%).19 In primary care settings, as many as 12% of patients meet criteria for either partial or full PTSD.20 In mental health treatment–seeking populations, the prevalence of PTSD may be as high as 40% to 50%, even among individuals being treated for other conditions and not seeking specialized trauma care.21

Exposure to potentially traumatizing events in the general population is the rule rather than the exception. In the National Comorbidity Survey (NCS), the lifetime prevalence of exposure to any traumatic event (based on DSM-III-R criteria) was 60% for men and 50% for women.17 The lifetime prevalence of exposure to any trauma increases to nearly 90% when the broader DSM-IV exposure criteria are employed.22 More than half of individuals with trauma exposure report exposure to more than one event.17 The median number of distinct traumatic events among individuals exposed to any trauma is nearly five.22

Events involving assaultive behavior (e.g., rape, military combat, kidnap/torture, physical assault, and molestation) are experienced by roughly 40% of the population, whereas other direct experiences of trauma (e.g., motor vehicle accidents, natural disasters, witnessing others being killed or injured, and being diagnosed with a life-threatening illness) have an estimated lifetime prevalence rate of 60%.22 Events that are only experienced indirectly (e.g., learning that a close friend or relative was assaulted or seriously injured) are reported by over 60% of the population. In fact, within this category, learning of the unexpected death of a close friend or relative is in itself associated with an exceedingly high lifetime prevalence (60%). The nature and type of trauma experienced by men and women differ considerably. NCS data for exposure to trauma are presented in Figure 34-1, A. Men more frequently report exposure to physical attacks, to combat, to being threatened with a weapon, to serious accidents, and to witnessing others being injured or killed.17 Men are twice as likely as women to be exposed to assaults, with nearly 35% being mugged or threatened with a weapon.22 Women more frequently report being raped, sexually molested, neglected as children, and physically abused. More than 40% of women have experienced interpersonal violence (including sexual violence and intimate partner violence).23 Exposure to all classes of trauma in both men and women peaks during late adolescence/early adulthood (ages 16 to 20).22 This is reflected in the median age of onset (23 years) for PTSD.24 Exposure to assaultive violence declines precipitously after this period, whereas all other classes of trauma exposure decline only modestly with advancing age, or not at all in the case of sudden unexpected death of a close friend or relative (an event that peaks in middle age). In general, the decline in all types of trauma following early adulthood appears to be steeper for women, suggesting that in women the risk of PTSD is especially pronounced during adolescence and early adulthood. The demographic variables of race, education, and income level do not appear to affect the risk of exposure to most types of trauma. The clear exception is assaultive violence, in which there is a twofold increase in exposure prevalence for nonwhites versus whites, for those with less education versus those with a college education, and for those with low incomes versus those with high incomes.22


Figure 34-1 A, Lifetime prevalence rates of trauma exposure based on gender and trauma type. B, Conditional probabilities of developing PTSD based on gender and trauma type.

(Data from Kessler RC, Sonnega A, Bromet E, et al: Posttraumatic stress disorder in the National Comorbidity Survey, Arch Gen Psychiatry 52:1048-1060, 1995.)

Despite the high prevalence of traumatic exposure, the development of PTSD is the exception rather than the rule. The overall conditional probability of PTSD after a traumatic event is 9.2%.22 However, the risk of PTSD varies substantially with the type of trauma experienced. Assaultive violence in general demonstrates the highest probability (over 20%) of leading to PTSD whereas learning about traumatic events to others carries the lowest probability (2%).22 Figure 34-1, B, illustrates the conditional PTSD probabilities associated with specific types of trauma for both men and women based on results from the NCS. Specific traumatic events that carry the highest conditional probability for PTSD include rape (50% or greater), torture/kidnap (50%), combat (nearly 40%), and childhood physical abuse or sexual molestation (25% to 50%).17,22 Women exposed to trauma are in general more than twice as likely (13% to 20%) to develop PTSD than are men (6% to 8%).17,22 This general twofold increase in risk of PTSD in women is maintained after controlling for the distribution of trauma types. However, women’s increased vulnerability to PTSD does not appear to be equally generalizable to all types of trauma. Specifically, the increased risk of a woman developing PTSD occurs predominantly after an assault, in which women demonstrate a PTSD risk with a probability of 35% (versus 6% in men).5 A significant portion of this sex difference appears to be attributable to the greater likelihood that women relative to men will meet the avoidance/numbing symptoms (DSM-IV Criterion C) required for the diagnosis.

Nearly 40% of all cases of PTSD result from assaultive violence, which reflects the high conditional probability of PTSD associated with this type of trauma.22 For men, combat exposure alone accounts for a sizeable percentage, approximately 30%, of PTSD.25 For women, sexual violence accounts for nearly 25% of all PTSD cases, and being “badly beaten up” (including intimate partner violence) constitutes an additional 20% of all cases of PTSD reported by women.5 Surprisingly, learning of the sudden, unexpected death of a close relative or friend accounts for the second highest proportion of overall PTSD cases (greater than 30%), a finding that reflects the extremely high prevalence for this type of event (60%) despite only a moderate conditional probability for PTSD (14%).22 Only 7% of all PTSD cases are attributable to other events related to learning about trauma to others. Approximately 23% of all PTSD cases result from direct exposure to nonassaultive events (e.g., accidents, natural disasters, and witnessing death).

As a final note in considering the rates of PTSD described above, it is important to recognize the “fluid” nature of epidemiological data, that is, reported prevalence rates are estimates that are not written in stone. Epidemiological studies of PTSD have shown that multiple methodological factors can affect the reported prevalence and risk rates of PTSD. Different diagnostic instruments (e.g., the Diagnostic Interview Schedule [DIS] versus the Structured Clinical Interview for DSM [SCID]) and data-gathering procedures (e.g., telephone versus in-person interview) can produce widely disparate prevalence estimates in the same population. Revisions to the diagnostic criteria as the DSM evolves can substantially alter overall rates of estimated trauma exposure and PTSD. Methodological variations in the documentation of traumatic events or the validation of symptom status or functional impairment can also have a significant impact on estimates. A recent reexamination of the well-known National Vietnam Veterans Readjustment Study (NVVRS) illustrates this point.26 The NVVRS is often cited for its estimate of a lifetime PTSD prevalence of 30.9% in Vietnam veterans.27 Employing the same database, the re-examination study provided a more systematic military record documentation of trauma exposure, differentiated war-related from prewar symptom onset, and factored in distress levels and severity of social/occupational impairment. Based on such refinements, the overall lifetime prevalence of PTSD in Vietnam veterans was reduced to 18.7%, nearly a 40% change from the original estimate. It is not known to what degree other accepted epidemiological “facts” may be challenged by future refinements. Recognizing the mutable and evolving nature of prevalence and risk estimates for PTSD has important implications regarding the establishment of future public health policy, as well as our understanding of the significance of such constructs as resiliency and “normative” response to trauma.


Psychiatric co-morbidity is the rule rather than the exception in PTSD. The percentage of a lifetime history of other psychiatric disorders in individuals diagnosed with PTSD has been estimated by the NCS at nearly 90% in men and 80% in women. In fact, nearly 60% of men and 45% of women with PTSD report more than three co-morbid psychiatric conditions.17 Major depressive disorder (MDD) is among the most common of co-morbid conditions for both men and women (affecting nearly 50%). Alcohol abuse (in the majority) and conduct disorder (over 40%) are also highly co-morbid in men. Additionally, there is a threefold to sevenfold increased risk for both men and women with PTSD to be diagnosed with other anxiety disorders, including generalized anxiety disorder (GAD), panic disorder, and specific phobias. High levels of psychiatric co-morbidity in PTSD may result from the substantial symptom overlap between PTSD and disorders such as MDD (with a loss of interest, social withdrawal, insomnia, and poor concentration) and other anxiety disorders (manifest by hyperarousal and avoidance). NCS results suggest that more often than not, PTSD is primary with respect to co-morbid affective disorders and substance abuse disorders, but secondary with respect to co-morbid anxiety disorders (and for men, co-morbid conduct disorder).17 Most studies have failed to find an increased risk of MDD or drug abuse for trauma-exposed individuals who are not diagnosed with PTSD.19 The same has been found for alcohol abuse or dependence in males, but not females. This suggests that MDD and substance abuse (with the exception of alcohol abuse in women) are not likely to be psychiatric conditions that independently occur outside of PTSD in response to trauma; rather they appear more likely either to be the result of PTSD (i.e., an emotional response to impairment and “self-medication” through substance abuse) or to share antecedent genetic or environmental factors (i.e., with a shared liability for both PTSD and depression/substance abuse).

Risk Factors

An understanding of relevant risk factors for the development of PTSD is complicated by the fact that independent risks may exist for an increased exposure to traumatic events and to an increased susceptibility for the development of PTSD once exposed to traumatic events. Research into the genetics of PTSD illustrates this complexity. Combat and civilian twin studies have estimated the genetic heritability of exposure to trauma as between 20% and 50%.28,29 Furthermore, exposure to different types of trauma may be differentially mediated by genetic factors. The likelihood of exposure to traumatic events involving assaultive violence appears to be highly influenced by genetics, whereas event exposure involving nonassaultive trauma appears to be largely nongenetic.29 It has been proposed that one pathway underlying genetic predisposition to traumatic exposure may be mediated through heritable personality traits (e.g., neuroticism, antisocial behavior, extroversion, and sensation seeking) that increase the risk of experiencing a traumatic event. It has been reported, for example, that the likelihood of experiencing a violent assault is predicted by antisocial personality traits, as well as the more nonpathological personality style of “being open to new ideas and experiences,” with genetic factors accounting for upwards of 10% of the relationship between personality and trauma exposure.30

Once exposed to a traumatic event, the conditional risk of PTSD also appears to be substantially influenced by genetics. Both combat and civilian trauma twin studies estimate the genetic heritability of PTSD to be approximately 30% to 40% after controlling for trauma exposure.29,31 Genetic heritability appears to be comparable among the three symptom clusters (i.e., re-experiencing, avoidance/numbing, and arousal). It remains unclear as to whether genetic factors for risk of PTSD are different for men and women or for different trauma types. Some preliminary gene studies have identified specific dopamine- or serotonin-transporter linked polymorphic regions that may be linked to PTSD susceptibility.32,33 However, these findings have yet to be fully replicated.

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