Post-Traumatic Stress Disorder
Anke Ehlers
Introduction
Clinicians have long noted that traumatic events can lead to severe psychological disturbance. At the end of the nineteenth and the beginning of the twentieth centuries, railway disasters, the World Wars, and the Holocaust prompted systematic descriptions of the symptoms associated with traumatic stress reactions. These include the spontaneous re-experiencing of aspects of the traumatic events, startle responses, irritability, impairment in concentration and memory, disturbed sleep, distressing dreams, depression, phobias, guilt, psychic numbing, and multiple somatic symptoms. A variety of labels were used to describe these reactions including ‘fright neurosis’, ‘combat/war neurosis’, ‘shell shock’, ‘survivor syndrome’, and ‘nuclearism’.(1, 2 and 3)
Whether the traumatic event can be considered a major cause of these psychological symptoms, has been the subject of considerable debate. Charcot, Janet, Freud, and Breuer suggested that hysterical symptoms were caused by psychological trauma, but their views were not widely accepted. The dominant view was that a traumatic event in itself was not a sufficient cause of post-trauma symptoms, and experts searched for other causes. Many suspected an organic cause. For example, damage to the spinal cord was suggested as the cause of the ‘railway spine syndrome’, microsections of exploded bombs entering the brain as the cause of ‘shell shock’, and starvation and brain damage as causes of the chronic psychological difficulties of concentration camp survivors. Others doubted the validity of the symptom reports and suggested that malingering and compensation-seeking (‘compensation neurosis’) was the major cause in most cases. Finally, the psychological symptoms were attributed to pre-existing psychological dysfunction. The predominant view was that reactions to traumatic events are transient, and that therefore only people with unstable personalities, pre-existing neurotic conflicts, or mental illness would develop chronic symptoms.(1, 2 and 3)
It was the recognition of the long-standing psychological problems of many war veterans, especially Vietnam veterans, that changed this view and convinced clinicians and researchers that even people with sound personalities can develop clinically significant psychological symptoms if they are exposed to horrific stressors. This prompted the introduction of post-traumatic stress disorder (PTSD) as a diagnostic category in DSM-III.(4) It was thus recognized that traumatic events such as combat, rape, man-made, or natural disasters give rise to a characteristic pattern of psychological symptoms. The diagnostic criteria specified the experience of a traumatic event as a necessary condition for the diagnosis. ICD-10(5) emphasized the causal role of traumatic stressors in producing psychological dysfunction even more clearly, in that a specific group of disorders, ‘reaction to severe stress, and adjustment disorders’, was created. These disorders are ‘thought to arise always as a direct consequence of the acute severe stress or continued trauma. The stressful event … is the primary and overriding causal factor, and the disorder would not have occurred without its impact’.
What makes a stressor traumatic?
In everyday language, many upsetting situations are described as ‘traumatic’, for example, divorce, loss of job, or failing an examination. However, a field study designed to establish what kinds of stressors lead to the characteristic symptoms of PTSD, showed that only 0.4 per cent of a community sample developed the characteristic symptoms of PTSD in response to such ‘low magnitude’ stressors.(6) Thus, in diagnosing PTSD, it appeared necessary to employ a strict definition of what constitutes a traumatic stressor.
Few people would contest that horrific events such as rape or bombings are traumatic. In an attempt to capture the essence of these stressors, the authors of DSM-IIIR required a traumatic stressor to be ‘outside the range of usual human experience’ and that it ‘would be markedly distressing to almost anyone’.(7) However, epidemiological studies showed that stressors that can lead to PTSD are actually quite common, for example road traffic accidents(8) or sexual assault.(9) Thus, the DSM-IIIR definition appeared too restrictive.
ICD-10 uses a broader definition and characterizes traumatic stressors by their exceptional severity and the distress they would cause for the average person ‘a stressful event or situation … of an exceptionally threatening or catastrophic nature, which is likely to cause pervasive distress in almost anyone’.(5) Thus, the ICD-10 diagnosis refers to a common sense understanding of which situations are likely to be extremely distressing.
In contrast, the authors of DSM-IV(10) attempted a specific definition. On the basis of research findings that threat to life or physical integrity during the event is one of the most consistent predictors of PTSD,(11) DSM-IV requires that the person ‘experienced, witnessed, or was confronted with an event or events that involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others’. The authors of DSM-IV made a further important step, in that they moved away from a purely situational definition and included the person’s subjective response to the situation as an additional criterion, requiring that the ‘person’s response involved intense fear, helplessness, or horror’ (or disorganized or agitated behaviour in the case of children).(10) The latter criterion takes into account that there is a large interindividual variability in the psychological response to the same situation.
The stressor criterion of DSM-IV is still under debate. Recent research suggests that both components of the definition may require extension. First, it may be necessary to include further possible emotional responses to traumatic stressors. There is accumulating evidence that emotional numbing during traumatic events is predictive of PTSD.(12) Furthermore, it has been established that perpetrators of violent crime sometimes develop PTSD. Witnessing or participating in war-related crimes such as torturing or killing prisoners of war and civilians and mutilation of corpses is more closely linked to PTSD in Vietnam veterans than the threat of death associated with combat.(13) The psychological state of the perpetrators during the events that later lead to PTSD has not been studied in detail, but it isdoubtful that they would meet the current DSM-IV definition. Feelings of shame or guilt that were experienced at the time or subsequently, may be predictive of PTSD in this group.(14)
Second, the emphasis on threat to life or physical integrity may omit important dimensions of subgroups of traumatic events. The threat to the perception of oneself as an autonomous human being may be a relevant dimension of traumatic events that involve intentional harm by other people.(15) Mental defeat, the perceived loss of all autonomy, was related to PTSD in political prisoners and assault victims,(15,16) independent of other indicators of trauma severity including threat to life and perceived helplessness.
Clinical features
The most characteristic symptoms of PTSD are the re-experiencing symptoms. Patients involuntarily re-experience aspects of the traumatic event in a very vivid and distressing way. This includes: flashbacks in which the person acts or feels as if the event were recurring; nightmares; and intrusive images or other sensory impressions from the event. For example, a woman who was assaulted kept seeing the eyes of the perpetrator looking through the letterbox before he broke into her house, and a man involved in a severe car crash at night kept hearing the sound of the impact. Despite these vivid memory fragments, intentional recall of the event is often disorganized, and some patients have amnesia for parts of the event (see also Chapter 4.6.3).
Reminders of the trauma arouse intense distress and/or physiological reactions and are consequently avoided, including conversations about the event. Patients try to push memories of the event out of their mind and avoid thinking about the event in detail, particularly about its worst moments. On the other hand, many ruminate excessively about questions that prevent them from coming to terms with the event, for example about why the event happened to them, about how it could have been prevented, or about how they could take revenge.
The patients’ emotional state ranges from intense fear, anger, sadness, guilt, or shame to emotional numbness. They often describe feeling detached from other people and give up previously significant activities. Various symptoms of hyperarousal include hypervigilance, exaggerated startle responses, irritability, difficulty concentrating, and sleep problems.
Classification
ICD-10(5) classifies PTSD (F43.1) among the reactions to severe stress and adjustment disorders (F43) that are primarily caused by stressful events. DSM-IV(10) classifies PTSD (309.81) among the anxiety disorders because symptom patterns, psychophysiological responses, family studies, and the efficacy of exposure treatment and serotonergic drugs suggested a relationship with other anxiety disorders. However, some of the symptoms would also suggest a relationship with dissociative disorders (e.g. amnesia) or depression (e.g. loss of interest).(17,18)
Diagnosis and differential diagnosis
Diagnostic criteria in ICD-10 and DSM-IV
Table 4.6.2.1 compares the diagnostic criteria of ICD-10 and DSM-IV.(10) ICD-10 research diagnostic criteria,(19) as well as diagnostic guidelines,(5) are included. The diagnostic systems agree on the core symptoms of PTSD (re-experiencing, avoidance, emotional numbing, and hyperarousal), but differ in the weight assigned to them. DSM-IV criteria are stricter.
Table 4.6.2.1 Diagnostic criteria for PTSD in ICD-10 and DSM-IV | ||||||||||||||||||||||||||||||||||||||||||||||
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DSM-IV puts a stronger emphasis on the avoidance/numbing cluster of symptoms by requiring a minimum of three of these symptoms.
DSM-IV states two additional criteria that are not included in ICD-10, namely a minimum symptom duration of 1 month and significant distress or impaired functioning.
A large-scale study(20) found a prevalence of ICD-10 PTSD of 6.9 per cent, and a prevalence of DSM-IV PTSD of 3 per cent.
Differential diagnoses
Differential diagnoses are summarized in Table 4.6.2.1. Distinguishing features include the following:
the type of stressor (adjustment disorders, enduring personality change)
the symptom pattern (adjustment disorders, enduring personality change)
the duration of the symptoms (acute stress disorder, acute stress reaction)
the question of whether the avoidance, numbing, and hyperarousal symptoms were present before the traumatic event occurred (other anxiety or depressive disorders)
the nature of the intrusive cognitions and perceptual disturbances (obsessive-compulsive disorder, psychotic symptoms, substanceinduced symptoms).
Prolonged repeated trauma, such as captivity or repeated childhood sexual abuse, may lead to a more complex pattern of symptoms, ‘complex PTSD’, that is characterized by somatization, dissociation, affect dysregulation, poor impulse control, selfdestructive behaviour, and pathological patterns of relationships.(21) It was debated whether to include a category ‘disorders of extreme stress not otherwise specified’ (DESNOS) into DSM-IV to accommodate these cases, but the decision was not to include it.(17) In ICD-10, the diagnosis ‘enduring personality changes after catastrophic experience’ covers such long-standing consequences of enduring trauma.
Furthermore, it is currently being debated whether an additional diagnostic category ‘traumatic grief’ should be included into the psychiatric classification systems.(22)
Ongoing research on symptom criteria
Some research has questioned the symptom clusters of DSM-IV. In particular, it may be preferable to assess the emotional numbing symptoms separately from the avoidance symptoms, because these symptoms do not load on the same factor in factor analyses and may have different underlying mechanisms. Furthermore, it may be preferable to include severity criteria for the symptoms rather than relying on counting the presence of symptoms.(23)
Assessment instruments
Several semi-structured interviews assess the DSM-IV criteria for PTSD. The most commonly used diagnostic interviews are the Structured Clinical Interview for DSM-IV (SCID)(24) and the Clinician Administered PTSD scale (CAPS).(25)
The most widely used self-report measure of PTSD symptoms used to be the Impact of Event scale.(26) The original scale contained two scales, an intrusion and an avoidance scale. It has been expanded to include an additional hyperarousal scale (IES-R).(27) The IES-R does not cover all the symptoms of PTSD specified in DSM-IV. This is why new measures that are modelled on the DSM-IV criteria are now commonly used in research studies, for example the Post-traumatic Stress Diagnostic scale (PDS)(28) or the PTSD Checklist (PCL).(29)
Epidemiology
The available epidemiological data so far stem mainly from large-scale studies in industrialized societies such as the United States or Australia. It remains to be investigated whether these data replicate in other countries. One has to bear in mind that the society and natural environment set conditions for exposure to traumatic events. For example, in the last decades, people in developing countries have had a much greater exposure to war and natural disasters than people in industrialized western societies.(30)
How common are traumatic events in the population?
Traumatic events are common. In a large representative United States’ sample, Kessler et al.(31) found that 60.7 per cent of the men and 51.2 per cent of the women had experienced at least one traumatic event meeting DSM-IIIR criteria in their lifetime. The most common types of trauma were witnessing someone being killed or severely injured, accidents, and being involved in a fire, flood, or natural disaster. Using DSM-IV criteria, Stein et al.(32) found a lifetime exposure to serious traumatic events of 81.3 per cent for men, and 74.2 per cent for women. Sudden death of a loved person was one of the most frequent traumatic stressors (DSM-IV criteria).(33)
What types of trauma are associated with high PTSD rates?
PTSD rates depend on the type of traumatic event. Rape was associated with the highest PTSD rates in several studies. For example, 65 per cent of the men and 46 per cent of the women who had been raped met PTSD criteria in the Kessler et al.(31) study. Other traumatic events associated with high PTSD rates included combat exposure, childhood neglect and physical abuse, sexual molestation; and for women only, physical attack and being threatened with a weapon, kidnapped, or held hostage. Accidents, witnessing death or injury, and fire or natural disasters were associated with relatively low-lifetime PTSD rates of less than 10 per cent.(31) Other research has shown high PTSD rates for torture victims,(34) survivors of the Holocaust,(35) and prisoners of war.(36) The emphasis in DSM-IV on threat to life or physical integrity has led to increasing awareness that medical illness and treatment (e.g. waking up during anaesthesia) can lead to PTSD.(37)
What proportion of people develop PTSD in response to a traumatic stressor?
Kessler et al.(31) found that the risk of developing PTSD after a traumatic event is 8.1 per cent for men, and 20.4 per cent for women. For young urban populations, higher risks have been reported; Breslau et al. found an overall risk of 23.6 per cent(38); 13 per cent for men and 30.2 per cent for women.(39)
The figures reported in these studies may be influenced by two types of biases that have opposite effects on probability estimates. First, Breslau et al.(33) have pointed out that previous studies overestimated the PTSD-risk imposed by traumatic events because participants reported on the worst trauma that they had experienced. When assessment focused on the symptoms induced by a traumatic event that was randomly selected from the ones that a person had experienced, the conditional risk of PTSD following exposure to trauma was found to be 9.2 per cent, using DSM-IV criteria.
Second, the retrospective methodology used in the epidemiological studies may have led to underestimation of PTSD rates due to selective recall. For example, the prevalence of PTSD 3 months after road traffic accidents was found to be around 20 per cent in prospective longitudinal studies,(40,41) whereas the retrospective studies found prevalences below 10 per cent.
How prevalent is PTSD in the population?
Kessler et al.(31) estimated that the lifetime prevalence of PTSD is 7.8 per cent, using DSM-IIIR criteria. Women had a higher prevalence than men (10.4 versus 5.0 per cent). This was due to both a greater exposure to high-impact trauma (rape, sexual molestation, childhood neglect, and childhood physical abuse) and a greater likelihood of developing PTSD when exposed to a traumatic event. Other studies using DSM-IIIR criteria have yielded similarly high prevalence rates.(9,39) Estimates for the 12-month prevalence range between 1.3 per cent in an Australian study(42) and 3.6 per cent in an US study.(43) A study using DSM-IV criteria and found a past-month PTSD prevalence of 2.7 per cent for women and 1.2 per cent for men.(32)
Earlier studies using DSM-III criteria had reported lower lifetime prevalences of about 1 per cent. Besides differences in procedures and sampling methods, the low PTSD prevalence in these earlier studies may be due to the use of an interview schedule with low sensitivity in detecting PTSD.(44) In particular, the early interviews asked global questions about the occurrence of traumatic events and lacked the repeated probing for specific events or event categories that seems to be necessary in eliciting relevant experiences.
Partial PTSD
Comorbidity of PTSD with other disorders and symptoms
PTSD shows a substantial comorbidity with affective disorders, other anxiety disorders, substance-use disorders, and somatization. In the study by Kessler et al.,(31) 88.3 per cent of the men and 78.1 per cent of the women with PTSD had comorbid psychiatric diagnoses. Studies of veterans with PTSD have also indicated an enhanced level of problems in family and marital adjustment and violent behaviour,(45) and heavy smoking.(46) Furthermore, reports of poor health and increased rates of various diseases, in particular infectious and nervous system diseases, are associated with PTSD.(47)
Is PTSD primary or secondary to the comorbid diagnoses? There is, as yet, little research into this question. The retrospective accounts obtained by Kessler et al.(31) suggested that PTSD was primary to comorbid affective or substance-use disorders in the majority of cases, and PTSD was primary to comorbid anxiety disorders in about half of the cases. Similarly, Breslau et al.(39) found that PTSD increased the risks for first-onset major depression and alcohol-use disorder. Conversely, pre-existing major depression also increased vulnerability to the PTSD-inducing effects of traumatic events and risk for exposure to traumatic events. A prospective study confirmed that PTSD increased the risk of subsequent pain, conversion symptoms, and somatization symptoms.(48)
Most of the comorbidity research has concentrated on the nature of the relationship between PTSD and alcohol or drug abuse. The majority of studies found that PTSD precedes the development of alcohol-abuse problems. There are probably several mechanisms for this relationship. In the short-term, alcohol is used to selfmedicate the symptoms of PTSD, but paradoxically intoxication and withdrawal symptoms may intensify the symptoms in the long-term.(49)
Summary of main findings from epidemiological studies
The majority of people will experience at least one traumatic event in their lifetime.
In assessing PTSD history, interviewers should probe for specific events.
Assault, in particular sexual assault, and combat have a higher impact than accidents and disasters.(31,32)
If the frequency and impact of traumatic events are considered together, sudden unexpected death of a loved one(33) and road traffic accidents(8) can be considered important causes of PTSD in western industrialized societies.
Men tend to experience more traumatic events than women, but women experience higher impact events.(31,32)
Women are at least twice as likely as men to develop PTSD in response to a traumatic event. This enhanced risk is not explained by differences in the type of traumatic event. The estimated lifetime prevalence for women is approximately 10 to 12 per cent, and for men 5 to 6 per cent.(9,31,38,39)
Comorbid depression and substance-use disorders appear to be secondary to PTSD in the majority of cases.
Aetiology
There is no single accepted theory of PTSD. Theoretical explanations have focused on psychological and biological mechanisms that are not mutually exclusive.
Psychological processes
(a) Fear conditioning
Mowrer’s two-factor conditioning theory of phobias has been applied to PTSD.(50, 51 and 52) It is suggested that through classical (Pavlovian) conditioning, stimuli that were present at the time of the trauma (unconditioned stimulus) become associated with fear and arousal responses. Subsequently, the conditioned stimuli trigger similar (conditioned) responses when presented on their own. Through stimulus generalization and higher-order conditioning, a wide variety of stimuli become triggers of distress in the aftermath of trauma. Quite naturally, the person will try to avoid the conditioned stimuli and the associated distress. The avoidance behaviour is negatively reinforced (operant or instrumental conditioning) because it leads to a reduction in psychological and physical discomfort. In the long-term, however, avoidance prevents extinction of the conditioned fear responses to reminders of the traumatic event, and thus maintains the problem.
(b) Personal meanings of the traumatic event and its aftermath
The persistence of PTSD symptoms has been explained by individual differences in the appraisal of the traumatic event: that is to say, in what personal meaning it has for them.(53, 54 and 55) Some people are able to see the trauma as a time-limited terrible experience that does not necessarily have negative global implications for their view of themselves, the world or the future. These people are likely to recover quickly. Individuals with persistent PTSD are characterized by excessively negative appraisals of the event that go beyond what everyone would find horrific about the event. The nature of predominant emotional responses in PTSD depends on the particular appraisals; for example, appraisals concerning danger lead to fear (‘Nowhere is safe’), appraisals concerning others violating personal rules lead to anger (‘Others have not treated me fairly’), appraisals concerning responsibility for the traumatic event lead to guilt or shame (‘It was my fault’, ‘I did something despicable’), and appraisals concerning loss lead to sadness (‘My life will never be the same again’).(55) Such appraisals distinguish between traumatized individuals with and without PTSD, and predict chronic PTSD.(16,56)
Negative appraisals involved in maintaining PTSD do not only concern the traumatic event itself, but also its sequelae such as the initial PTSD symptoms or responses of other people in the aftermath of the traumatic event.(55,57,58) In line with this hypothesis, negative interpretations of intrusive recollections (e.g. ‘I am going mad’) after road traffic accidents were one of the most important predictors of PTSD at 1 year after the event.(41) Perceived negative responses from other people in the aftermath of trauma predicted PTSD in studies of assault and torture victims.(15,16)
(c) Nature of trauma memories
What exactly distinguishes trauma memories from other memories and what explains the distressing re-experiencing symptoms in PTSD is still under debate.(59,60) Phenomenological observations show that although a wide range of stimuli can trigger unwanted intrusive memories of parts of the traumatic event, people with PTSD show relatively poor intentional recall of details such as the order of events and their recall appears disjointed.(60) Several theories have been put forward to explain re-experiencing symptoms. Foa and colleagues(53,58) explain re-experiencing as spreading activation in a pathological network in memory. This network is thought to be particularly large and easily triggered. It contains many stimulus propositions that are erroneously linked to danger, causing fear responses to harmless stimuli associated with the traumatic event in memory. In addition, the person’s reactions during the trauma are linked to the belief that the self is incompetent. Activation of components of the trauma memory (for instance, by confrontation to a reminder, by similar bodily sensations, or by thinking about the event) will activate the whole network, including the emotional responses that the person had during the traumatic event.
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