Acute Stress Reactions
Anke Ehlers
Allison G. Harvey
Richard A. Bryant
Introduction
Exceptionally stressful life events can cause severe psychological symptoms, including anxiety, feelings of derealization and depersonalization, and hyperarousal. In one of the first studies to comprehensively document acute reactions to extreme stress, Lindemann(1) observed that the symptoms reported by survivors of the Coconut Grove Fire included avoidance, re-experiencing scenes from the fire, reports of derealization, and the experience of anxiety when exposed to reminders of the event. Similarly, acute responses reported by soldiers who fought in the First and Second World Wars included re-experiencing symptoms and dissociative responses such as numbing, amnesia, and depersonalization.(2)
The International Classification of Diseases has recognized acute stress reactions since 1948 (ICD-6).(3) In the most recent edition (ICD-10),(4) early reactions to exceptionally stressful life events are diagnosed as acute stress reaction, one of the diagnoses in the section headed ‘reactions to severe stress, and adjustment disorders’.
In contrast, the Diagnostic and Statistical Manual of Mental Disorders did not formally recognize that exceptionally stressful life events are a sufficient cause of psychological symptoms until 1980 when its third edition (DSM-III)(5) introduced the diagnosis of post-traumatic stress disorder (PTSD). DSM-III did not stipulate a duration for the symptoms, but the revised third version (DSMIII-R)(6) required that the symptoms of PTSD must be present for more than 1 month after the traumatic event. This stipulation precluded the inclusion of acutely traumatized individuals who instead were diagnosed with adjustment disorder.(7) In 1994 the fourth edition of DSM (DSM-IV)(8) formally recognized acute trauma reactions by introducing the new diagnosis of acute stress disorder into the anxiety disorders section.
The diagnoses of acute stress reactions in ICD-10 and of acute stress disorder in DSM-IV have similarities in that they are caused by extreme stress and have some overlap in symptom patterns. They can be considered as two separate points on a continuum from transient to more enduring symptoms. However, there are also differences in the underlying concepts, as we will discuss in this chapter.
Clinical features
Acute stress reactions, as defined in ICD-10, are transient reactions to exceptional physical and/or mental stress. There is an initial stage of a ‘daze’, including narrowing of attention, inability to comprehend stimuli, and disorientation. This is followed by a rapidly changing picture of symptoms that may include withdrawal from the surrounding situation, flight reactions, panic anxiety, and autonomic hyperarousal, depression, anger, or despair. Symptoms usually begin to diminish after 24 to 48 h and should be minimal after about 3 days.
In contrast, acute stress disorder, as defined in DSM-IV, is only diagnosed if the psychological symptoms persist for more than 2 days. Dissociative symptoms dominate the disorder. Dissociation refers to a disruption of the usually integrated feelings of consciousness, memory, identity, or perception of the environment. Symptoms include a subjective sense of numbing or detachment, reduced awareness of surroundings, derealization, depersonalization, or dissociative amnesia. In addition, patients with acute stress disorder experience symptoms that are typical of PTSD, namely re-experiencing aspects of the event, avoidance of reminders of
the event, and hyperarousal symptoms. Acute stress disorder is seen in DSM-IV as a precursor of PTSD. If the re-experiencing, avoidance, and hyperarousal symptoms persist for more than 4 weeks, PTSD is diagnosed.
the event, and hyperarousal symptoms. Acute stress disorder is seen in DSM-IV as a precursor of PTSD. If the re-experiencing, avoidance, and hyperarousal symptoms persist for more than 4 weeks, PTSD is diagnosed.
Classification
ICD-10 classifies acute stress reactions (F43.0) among the reactions to severe stress and adjustment disorders (F43) that are primarily caused by stressful events. DSM-IV classifies acute stress disorder (308.3) among the anxiety disorders, like PTSD (see also Chapter 4.6.2).
Diagnosis and differential diagnosis
The main diagnostic criteria for acute stress reactions (ICD-10) and acute stress disorder (DSM-IV) are compared in Table 4.6.1.1.
Stressor criterion
Both ICD-10 and DSM-IV require that acute stress responses must occur in the immediate aftermath of an exceptionally stressful event. ICD-10 uses a broad concept of what qualifies as an ‘exceptional mental or physical stressor’. This includes stressors that would be regarded as traumatic (e.g. rape, criminal assault, natural catastrophe) as well as unusually sudden changes in the social position and/or network of the individual (e.g. domestic fire or multiple bereavement). In contrast, DSM-IV uses a narrow definition of stressors that lead to acute stress disorder, which is identical to the stressor criterion of PTSD. It requires (i) that the traumatic event must have involved actual or threatened death or serious injury, or a threat to the physical integrity of self or others, and (ii) that the person’s response to the traumatic event must have involved intense fear, helplessness, or horror (or disorganized or agitated behaviour in children) (see Chapter 4.6.2 for the rationale underlying this definition).
Symptom patterns
As shown in Table 4.6.1.1, the diagnostic criteria for acute stress reactions (ICD-10) and acute stress disorder (DSM-IV) overlap, in that they include symptoms of dissociation, anxiety, and hyperarousal. DSM-IV puts a much greater emphasis on dissociation, requiring a minimum of three of the dissociative symptoms speci.ed in Table 4.6.1.1 (Criterion B). According to ICD-10, any combination of a minimum of four symptoms of generalized anxiety disorder (specified in Criterion C, Table 4.6.1.1) would be sufficient to establish the diagnosis of acute stress reaction. In addition, DSM-IV, but not ICD-10, requires the individual to have at least one re-experiencing symptom, to show marked avoidance of reminders of the trauma, and to experience significant distress or impairment of functioning.
In contrast to DSM-IV, ICD-10 distinguishes between mild, moderate, and severe forms of acute stress reactions on the basis
of additional symptoms (Criterion C, additional symptoms, Table 4.6.1.1) such as social withdrawal, hopelessness, or excessive grief. A mild severity is stipulated when none of these symptoms are present, moderate when two are reported, and severe when four are reported or when there is dissociative stupor.
of additional symptoms (Criterion C, additional symptoms, Table 4.6.1.1) such as social withdrawal, hopelessness, or excessive grief. A mild severity is stipulated when none of these symptoms are present, moderate when two are reported, and severe when four are reported or when there is dissociative stupor.
Table 4.6.1.1 Comparison of the criteria for acute stress reaction (ICD-10) and acute stress disorder (DSM-IV) | ||||||||||||||||||||||||
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Time course of symptoms
The two diagnoses cover distinct periods on a continuum from transient to more persistent symptoms. Specifically, to meet the criteria for an acute stress reaction (ICD-10), symptoms must be manifest within 1 h of the stressor (Criterion B) and begin to diminish after no more than 8 h for a transient stressor and after no more than 48 h for an enduring stressor (Criterion D).
The diagnostic criteria for acute stress disorder (DSM-IV) require that the disturbance must last for a minimum of 2 days and a maximum of 4 weeks post-trauma, after which a diagnosis of PTSD can be considered.
Assessment instruments
There are two recognized clinician-administered and two selfreport measures of acute stress disorder (DSM-IV) available. As yet, there are no established standardized assessment instruments for transient acute stress reactions (ICD-10).
(a) Acute stress disorder interview
This structured clinical interview establishes the presence or absence of 19 symptoms of acute stress disorder.(9) The sum of the symptoms scored as being present indicates acute stress disorder severity. This measure has very good internal consistency (r = 0.90), and, with clinician-based diagnoses as the criterion, very good sensitivity (91 per cent) and specificity (93 per cent). Test–retest reliability is strong (r = 0.88).
(b) Structured clinical interview for DSM-IV (SCID(10))
The SCID interview indexes the presence, absence, or subthreshold presence of each acute stress disorder symptom specified in DSM-IV. An advantage of employing this interview is that it provides a comprehensive assessment of the differential diagnoses and comorbid disorders that can be present in trauma populations.
(c) Stanford acute stress reaction questionnaire(11)
This self-report inventory asks patients to rate the frequency of a range of dissociative, intrusive, somatic anxiety, hyperarousal, attention disturbance, and sleep disturbance symptoms. The questionnaire has very good internal consistency (Cronbach’s alpha = 0.90 and 0.91 for dissociative and anxiety symptoms, respectively) and concurrent validity with scores on the Impact of Event Scale (r = 0.52 to 0.69).(12,13) It can be employed as a measure of the severity of symptoms, but does not allow the diagnosis of acute stress disorder to be established as it has not yet been validated against clinician diagnoses.
(d) Acute stress disorder scale(14)
This self-report scale is scored on a 5-point scale that reflects degree of severity of 19 acute stress disorder symptoms. The Acute Stress Disorder Scale possesses good sensitivity (95 per cent) and specificity (83 per cent) relative to the Acute Stress Disorder Interview. Test–retest reliability with a re-administration interval of 2 to 7 days is strong (r = 0.94).(14)
Differential diagnoses
Both ICD-10 and DSM-IV require that the symptoms are not merely an exacerbation of a pre-existing disorder. In addition, a number of alternative diagnoses need to be considered.
(a) Post-traumatic stress disorder
In ICD-10, PTSD is conceptualized as an alternative diagnosis of acute stress reactions. The definitions of acute stress reaction and PTSD differ in terms of the stressor criterion (exceptionally stressful life event versus exceptionally threatening or catastrophic event), the time course (symptoms start to diminish within 48 h versus no time limit), and symptom pattern (PTSD, but not acute stress reaction, includes involuntary re-experiencing the traumatic event).
In DSM-IV, acute stress disorder can be distinguished from PTSD by the time-frame covered by the diagnoses. Acute stress disorder refers to the period from 2 days to 1 month post-trauma, after which a diagnosis of PTSD can be considered. The primary difference between the symptom criteria for acute stress disorder and PTSD in DSM-IV is the former’s emphasis on dissociative reactions.
(b) Adjustment disorder
This diagnosis covers a wide range of emotional or behavioural symptoms indicative of distress, which are judged to be out of proportion to the stressor experienced. This broad coverage can be contrasted with (i) the specific set of symptoms described by the acute stress disorder and acute stress reaction criteria, and (ii) the stipulation that the stressor involves both a threat to life and a subjective response of fear for the acute stress disorder and an exceptional stressor in the case of acute stress reaction.
(c) Brain injury
A number of acute stress disorder symptoms overlap with symptoms of brain injury including reduced awareness, depersonalization, derealization, irritability, and concentration difficulties.(15) While results from neuropsychological and neurological investigations may assist in the differential diagnosis, there appear to be a group of individuals with a mild head injury for whom there are no known tools to differentiate whether the disturbance is due to brain injury or acute stress disorder, or whether both are present.
(d) Brief psychotic disorder
When there is one or more psychotic symptoms present after experiencing an extreme stressor, the brief psychotic disorder diagnosis should be considered.
(e) Dissociative disorders
Given the emphasis on dissociative symptoms in acute stress disorder, it needs to be distinguished from dissociative amnesia and depersonalization disorder. The criteria for these diagnoses stipulate that if the amnesia or depersonalization can be accounted for by acute stress disorder then a dissociative disorder cannot be diagnosed (see Chapter 5.2.4).
Epidemiology
Incidence
There is little research into what proportion of people develop acute stress reactions to severe stress. In a study of accident survivors, 14 per cent experienced a response pattern characterized by
derealization, and a further 17 per cent exhibited strong anxiety or dysphoria.(16)
derealization, and a further 17 per cent exhibited strong anxiety or dysphoria.(16)
Estimates of the incidence of acute stress disorder range from about 14 per cent in motor vehicle accident survivors to 33 per cent in witnesses of a mass shooting.(17) Given the variable procedures and assessment tools employed across studies, it is difficult to determine whether the different rates of acute stress disorder detected are attributable to differences in method or in the type of trauma.
Comorbidity
Data on comorbidity are sparse. Given the similarities between acute stress disorder and PTSD it is likely that the conditions found to be comorbid with PTSD, in particular depression and substance abuse, will be applicable to acute stress disorder (see Chapter 4.6.2).
Aetiology
Both psychological and biological theories have attempted to explain the symptoms of acute stress disorder. They overlap largely with theories of PTSD (see Chapter 4.6.2). Given that acute stress reaction describes a transient disturbance, there are no specific theories of acute stress reactions as defined in ICD-10.
Psychological theories
The psychological mechanism that has received the most attention in relation to acute stress disorder is dissociation, as reflected in the DSM-IV criteria. It has been argued that dissociation minimizes the adverse emotional consequences of trauma by restricting awareness of the experience to avoid overwhelming fear and loss of control.(13) Dissociation is thought to prevent recovery because it prevents the integration of the traumatic experience into existing schemas(18) and it prevents the full activation of the trauma memory which is thought to be necessary for its modification.(19) In line with these hypotheses, dissociation during or immediately after a traumatic event predicts PTSD.(20) In contrast, an alternate view posits that dissociation at the time of trauma may serve a protective function because it may limit the encoding of aversive experiences and this may assist adaptation.(21) Consistent with this view, there is evidence that persisting dissociation (which is a form of cognitive avoidance) is more predictive of PTSD than dissociation that occurs at the time of trauma.(22,23)
Psychological theories of acute stress disorder and PTSD focus on the personal meaning of the trauma and its consequences, and characteristics of the trauma memory. Several hypotheses about the problems in memory that are responsible for the characteristic re-experiencing symptoms (i.e. unwanted memories of aspects of the trauma that occur in response to a wide range of stimuli) have been suggested (see also Chapter 4.6.2). Foa and colleagues(24,25) suggested that PTSD is characterized by a pathological network in memory that is particularly large and easily triggered. It contains many stimulus propositions that are erroneously linked to danger, causing fear responses to harmless stimuli that are associated with the traumatic event in memory. Brewin et al.(26) postulated that two different representations of the trauma are formed in memory. The first, termed verbally accessible memory, contains the conscious recollection of the trauma. The second memory representation, termed situationally accessible memory, comprises sensory, physiological, and motor aspects of the trauma in the form of codes that enable the re-experiencing of the original experience. Ehlers and Clark(27) suggested three memory processes to explain that a wide range of stimuli can trigger vivid memories and strong emotional responses, which are experienced as if the traumatic event was happening at present. First, trauma memory is thought to be inadequately linked to its context in memory, which leads to poor inhibition of stimulus-driven retrieval. Two other basic memory processes, perceptual priming and associative learning, are thought to further enhance the chances of stimulus-driven retrieval of memories. Consistent with these psychological theories, there is evidence that chronic PTSD is predicted by impaired access to autobiographical memories(28) and the perceived ‘nowness’ of trauma memories.(29) There is also evidence that maladaptive appraisals such as ‘I am inadequate’, ‘My reactions since the trauma mean I am losing my mind’, or ‘I have permanently changed for the worse’ in the acute phase after trauma exposure predict chronic PTSD.(30,31)
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