A cognitive model of posttraumatic stress disorder - summary of an article by Ehlers & Clark (2000)

A cognitive model of posttraumatic stress disorder
Ehlers, A., & Clark, D.M. (2000)
Behaviour Research and Therapy, 38, 319-345.

Abstract

PTSD becomes persistent when individuals process trauma in a way that leads to a sense of serous, current threat. This sense of threat arises as a consequence of: 1) excessively negative appraisals of the trauma and/or its sequelae 2) a disturbance of autobiographical memory. This is characterized by poor elaboration and contextualisation, strong associative memory and strong perceptual priming.

Change in the negative appraisals and trauma memory are prevented by a series of problematic behavioural and cognitive strategies.

Symptoms of posttraumatic stress disorder (PTSD) include: 1) repeated and unwanted re-experiencing of the event 2) hyperarousal 3) emotional numbing 4) avoidance of stimuli (including thoughts) which could serve as reminders for the event.

A cognitive model of PTSD

Overview

PTSD occurs only if individuals process the traumatic event and/or its sequealae in a way which produces a sense of serious current threat.

Two processes lead to a sense of current threat 1) individual differences in the appraisal of the trauma and/or its sequelae 2) individual differences in the nature of the memory for the event and its link to other autobiographical memories.

Once activated, the perception of current threat is accompanied by intrusions and other reexperiencing symptoms, symptoms of arousal, anxiety and other emotional responses.

The perceived threat motivates a series of behavioural and cognitive responses that are intended to reduce perceived threat and distress in the short-term, but have the consequence of preventing cognitive change and maintaining the disorder.

Appraisal of the trauma and/or its sequelae

Individuals with PTSD are unable to see the trauma as a time-limited event that does not have global negative implications for their future. These individuals are characterized by idiosyncratic negative appraisals of the traumatic event and/or its sequelae that have the common effect of creating a sense of serous current threat. This threat can be external or internal (for example: threat to one’s view of oneself as a capable person).

Appraisal of the traumatic event

Several types of appraisal can produce a sense of current threat: 1) individuals may overgeneralise from the event, as a consequence perceive a range of normal activities as more dangerous than they really are 2) exaggerate the probability of further catastrophic events as general, or think that they ‘attract disaster’.

Appraisals of the way one felt or behaved during the even can have long-term threatening implications.

Appraisals of the traumatic sequelae

A variety of idiosyncratic, negative appraisals of the sequelae of the traumatic event can produce as sense of current threat and contribute to persistent PTSD: 1) interpretation of one’s initial PTSD symptoms 2) interpretation of other people’s reactions in the aftermath of the event 3) appraisal of the consequences that the trauma has in other life domains.

Symptoms that are common shortly after a traumatic event are 1) intrusive recollections and flashbacks, 2) irritability and mood swings 3) lack of concentration and numbing.

If individuals do not see common symptoms as a normal part of the recovery process, they may interpret them as indications that they have permanently changed for the worse, or as indicators of threat to their well being.

Such appraisals maintain PTSD by directly producing negative emotions and by encouraging individuals to engage in dysfunctional coping strategies that have the effect of enhancing PTSD symptoms.

Other people are often uncertain about how they should respond to a trauma victim and may avoid talking about the event in order not to distress the victim. This may be interpreted as a sign that others don’t care or that they think the event was partly the victims fault. Such interpretations are likely to directly produce estrangement for mothers and social withdrawal.

Appraisals and emotional responses

The nature of predominant emotional responses in persistent PTSD depends on the particular appraisals: 1) appraisals concerning perceived danger lead to fear 2) appraisals concerning others violating personal rules and unfairness lead to anger 3) appraisals concerning one’s responsibility for the traumatic event lead to guilt 4) appraisals concerning one’s violation of important internal standards lead to shame 5) appraisals concerning perceived loss lead to sadness.

Most patients with persistent PTSD experience a range of negative emotions. Different appraisals are activated at different times. The degree of conviction varies from time to time.

Memory for the traumatic event

Patients often have difficulty intentionally retrieving a complete memory of the traumatic event. This intentional recall is fragmented and poorly organized. Details may be missing and they have difficulty recalling the exact temporal order of events.

Patients report a high frequency of involuntarily triggered intrusive memories involving re-experiencing aspects of the event in a vivid and emotional way. Involuntary re-experiencing has a number of important characteristics: 1) it mainly consist of sensory impressions, rather than thoughts. They are predominantly visual 2) the sensory impressions are experienced as if they were happening right now rather than being memories from the past and the emotions accompanying are the same as those experienced at the time. They lack the awareness of remembering that usually characteristics autobiographical memories 3) The original emotions and sensory impressions are re-experienced even if the individual later acquired new information that contradicted the original impression or if (s)he knows that the impression did not turn out the be true 4) Affect without recollection. Individuals with PTSD sometimes re-experience physiological sensations or emotions that were associated with the traumatic event without a recollection of the event 5) the involuntary re-experiencing of the traumatic event is triggered by a wide range of stimuli and situations. Many of the trigger stimuli are cues that don’t have a strong semantic relationship to the traumatic event, but were temporally associated with the event.

The intrusion characteristics and the pattern of retrieval that characterises persistent PTSD is due to the way trauma is encoded and laid down in memory.

Poor elaboration and incorporation into autobiographical memory base

There are two routes to the retrieval of autobiographical information 1) through higher-order meaning-based retrieval strategies 2) through direct triggering by stimuli that were associated with the event.

Much of the normal processing of autobiographical memories has the function of reducing the ease with which memories of past experiences are unintentionally retrieved while engaging in everyday tasks.

Autobiographical events are usually incorporated into an autobiographical memory knowledge base that is organized by themes and personal time periods. This enhances the first retrieval route and inhibits the second. This has the effect that when an autobiographical memory enters consciousness, it comprises both specific information about the event and general information about the lifetime period that the event took place in and abstracted information about the type of event in general.

In persistent PTSD one of the main problems is that the trauma memory is poorly elaborated and inadequately integrated into its context in time, place, subsequent and previous information and other autobiographical memories. This explains problematic intentional recall, the ‘here and now’ quality, the absence of links to subsequent information, and the easy triggering by physical similar cues.

Strong S-S and S-R associations

A problem in persistent PTSD is that S-S and S-R associations are particularly strong for traumatic material. This makes triggering of memories of the event or emotional responses by associated stimuli more likely.

Two aspects of S-S and S-R learning are of interest 1) the form of learning helps the organism in making predictions about what will happen next. In PTSD, distinct stimuli that were present shortly before or during the traumatic event become associated with the default prediction of severe danger to self. 2) retrieval from associated memory is cue driven and unintentional. The individual may not be aware of the triggers individuals may not be aware that his or her reaction is due to activation of the traumatic memory

Failure to spot the origin of the re-experiencing symptoms makes it difficult for the client to learn that there is no present danger when exposed to the triggers.

Strong perceptual priming

There is strong perceptual priming for stimuli that were temporally associated with the traumatic event. There is a reduced perceptual threshold for these stimuli. cues that were associated with the trauma and that consequently can direct trigger the trauma memory are more likely to be noticed.

Implicit memory traces are not well discriminated form other memory traces. Vague physical similarity would be sufficient in perceiving stimuli as similar to those occurring in the traumatic situation, thus triggering symptoms.

Relationship between the nature of trauma and trauma appraisals

There is a reciprocal relationship between the nature of the trauma memory and the appraisals of the trauma. When individuals with persistent PTSD recall the traumatic event, their recall is biased by their appraisals. Individuals selectively retrieve information that is consistent with appraisals.

Inability to remember details of the trauma can be appraised in a way that maintains the sense of current threat.

The here and now quality of the emotions that are associated with the trauma memory can contribute to problematic appraisals.

In those with persistent PTSD for whom the traumatic event has seriously threatened their view of themselves, the general organisation of their autobiographical memory knowledge based may be disturbed. They seem unable to reorganize their previous and subsequent experiences in a way which produces a stable view of themselves and the context they liv in. This produces a sense of disorientation and will have the effect that their retrieval from memory will be less filtered by current context and more cue-driven.

Maladaptive behavioural strategies and cognitive processing styles

When patients with PTSD perceive a serous current threat and the accompanying symptoms, they try to control the threat and symptoms by a range of strategies. This strategies are meaningfully linked with the individual’s appraisals of the trauma.

Strategies to control the threat/symptoms are maladaptive. They maintain PTSD by three mechanisms: 1) directly producing PTSD symptoms 2) preventing change in negative appraisals of the trauma and/or its sequelae 3) preventing change in the nature of the trauma memory.

Cognitive strategies that increases symptoms are: 1) thought suppression. If patients try to push thoughts out of their mind, this increases the frequency of unwanted recollection 2) behaviours used to control some of the PTSD symptoms may increase others 3) selective attention to threat cues.

Strategies that prevent a change in the appraisal of the traumatic event are: 1) safety behaviours, actions individuals take to prevent or minimize anticipated further catastrophes They prevent disconfirmation of the belief that the catastrophe will occur if one doesn’t engage in preventative action 2) avoidance of reminders of the trauma. Prevents correction of appraisals about how the even could have been avoided 3) Rumination about the trauma and its consequences, thought to be driven by problematic appraisals.

Strategies preventing change in the nature of the trauma memory are: 1) actively trying not to think about the event, individuals with PTSD try to keep their mind constantly occupied  or think about the even in a non-emotional way. These efforts prevent individuals form elaborating the trauma memory and linking their experience in its context in time, space, previous and subsequent information and other autobiographical memories. They also prevent changes in appraisals. 2) avoidance of reminders of the trauma. They often provide retrieval cues for inaccessible details, avoidance interferes with formation of more elaborative trauma memory. 3) Use of alcohol or medication to control anxiety 4) give up or avoid activities 5) Dissociation, derealisation, depersonalisation, and emotional numbing may impede the elaboration of the trauma memory and its integration into the autobiographical memory base.

Cognitive processing during trauma

The two processes that lead to a sense of current threat (appraisals of the trauma/its sequelae and the nature of trauma memory) are influenced by the type of cognitive processing during the traumatic event.

Influences on appraisal

Mental defeat is a correlate to chronic PTSD and poor response to treatment. It is the perceived loss of all psychological autonomy, accompanied by the sense of not being human any longer.

Patients who experienced mental defeat are more likely to interpret the trauma as evidence for a negative view of themselves.

Influences on memory

The nature of trauma memory depends on the quality of processing at encoding.

Encoding can be conceptual or data-driven. The degree of conceptual processing (processing the meaning of the situation, in an organized way and placing it into context) during a traumatic event determines the nature of the memory and the ability to intentionally retrieve information from the memory.

If the individual engages mainly in data-driven processing (processing the sensory impressions), the trauma will be relatively difficult to retrieve intentionally and there will be strong perceptual priming for accompanying stimuli. The memory trace will be poorly discriminated from other memory traces. This impairs stimulus discrimination between stimuli present during the trauma and harmless stimuli.

Unorganized memories observed in PTSD may in part result from an inability to establish a self-referential perspective while experiencing the trauma that can be integrated into the continuum of other autobiographic memories in time.

Dissociation during trauma explains the fragmentation of traumatic memories. Some components of dissociation may overlap with the concepts of conceptual vs data-driven processing and lack of self-referential perspective when encoding. Emotional numbing may interfere with the formation of an organized memory.

Propositions are stored in long-term memory with a default ‘true’ value. During a traumatic event, individuals may not have enough cognitive capacity to decide that some very threatening aspects of the trauma are not true.

Trauma characteristics, previous experiences and beliefs, current state

There are several background factors that are likely to influence cognitive processing during the traumatic event, the nature of trauma memory, the appraisals and the coping strategies. These factors are neither necessary nor sufficient in the etiology of PTSD. (This is not an exhaustive list)

Cognitive processing during a trauma event will depend on: 1) characteristics of the trauma, like duration and predictability 2) previous experience of trauma and coping styles used during these events. Trauma may reactivate memories of abuse when someone engaged in data-driven processing, and does this again 3) low intellectual ability, may be related to less conceptual processing 4) Prior beliefs 5) state factors, such as alcohol, exertion or arousal.

Appriasals of the trauma and its sequelae will be influenced by: 1) characteristics of the event and its sequelae, for example, having no control at all may be interpreted as a lack of control in general 2) prior beliefs 3) prior experiences

Cognitive and behavioural strategies used to control PTSD and current threat are likely to be influenced by prior experiences and beliefs.

Features of PTSD explained by the model

Delayed onset of PTSD

Delayed onset occurs either because some later event gives the original trauma or its sequelae a much more threatening meaning or because some of the stimuli that are particularly potent reminders of the traumatic event were not available until some time afterwards.

Anniversary reactions

Around anniversaries, patients are confronted with many external reminders and they generate internal retrieval cues by dwelling on what their lives were like before the traumatic event and about their feelings and experiences on the day, before the traumatic event happened. Anniversaries often are taken as landmarks for negative appraisals, which activate strategies.

Frozen in time

Patients with PTSD day they feel locked into the past, unable to resume their life. This has three sources 1) it is related to appraisals of the trauma 2) continually re-experiencing sensation and emotions they had at the time of the trauma in their original form, disconnects them from current reality 3) giving up or avoiding activities that were important to the person before the traumatic event contributes to the sense that time has stood still.

Sense of impending doom

The sense that worse is to come is explained by the nature of the trauma memory. Sensory information and emotions are retrieved form the memory without the time-perspective of ‘remembered’ emotions, thus leading to the perception of future threat. Intrusive memories are about warning signals that during the traumatic event predicted the occurrence of worst moments. The poor ability to retrieve details or order of events during trauma together with the intrusive nature of the memories may be interpreted as indicating that something even worse happened.

No benefit from taking/thinking about the trauma

This is because of the way they think and talk about the event. Thinking often takes the form of rumination about ‘what if...’. Talking is done in a non-emotional way.   This prevents proper access to the meaning of the event and its contextualisation.

Treatment implications

Putting the trauma into the past requires change in three areas: 1) the trauma memory needs to be elaborated and integrated into the context of the individuals preceding and subsequent experience in order to reduce intrusive re-experiencing 2) problematic appraisals of the trauma and/or its sequelae that maintain the sense of current threat need to be modified 3) dysfunctional behavioural and cognitive strategies that prevent memory elaboration, symptoms or hinder reassessment of problematic appraisals need to be dropped.

Assessment

A key aim of the assessment interview is to identify the main cognitive themes that will be addressed in therapy.

Parts of the memory that currently elicit particularly strong distress are explored to identify meanings, as are intrusive images and moments when the patient dissociates. The nature of predominant emotions is an invaluable clue to cognitive themes.

It is useful to ask what has been most distressing since the event and to explore patients’ beliefs and their symptoms.

An aim of the assessment interview is to start to characterize the nature of the trauma memory and the spontaneous intrusions. Key issues include: the extent to which there are gaps in memory, whether the sequence of events seems muddled or confused and the extent to which the memory/intrusions have a ‘here and now’ quality and strong sensory and motor components.

Rationale for treatment

The rationale for treatment has three elements: 1) it is explained that PTSD symptoms are a common initial reaction to an abnormal event 2) many of the ways the patient has so far used to deal with the trauma memory may have been useful for coping with other, milder stressors, but may be maintaining their symptoms in this instance 3) treatment involves fully processing the trauma and reversing their remaining factors.

A key element of treatment will involve thinking about the trauma more and discussing it in detail.

Thought suppression experiment

A thought suppression experiment can be a useful way of illustrating the consequences of this strategy.

Education

Education about police, ambulance, hospitals and other matters may help correct problematic appraisals.

Reclaiming one’s life

Often minor changes can help reduce the feeling of being stuck in time. When planning reactivation of activities, it is important to identify problematic beliefs that may prevent the patient from complying.

Reliving with cognitive restructuring

Reliving has important functions: 1) it promotes the elaboration and contextualisation of the trauma memory 2) identifying and discussing not spots during reliving is useful in identifying the idiosyncratic appraisals of the trauma 3) imagined reliving is a behavioural experiment to test negative expectations.

To help patients to stay with the memory, the therapist asks questions. It usually involves the whole event, but as therapy progresses, it focuses more exclusively on hot spots.  

After a reliving exercise, problematic thoughts and beliefs are discussed, using relevant cognitive restructuring techniques. Once an alternative perspective has been identified, efforts are made to incorporate this information into the next reliving.

As therapy progresses, the nature of trauma memory often changes.

Patients who are particularly likely to require extensive verbal and imagery cognitive restructuring are those who: experience anger, guilt or shame as a predominant emotion, interpret their behaviour or emotions during the event as showing something negative about themselves and experienced violence over a prolonged period of time.

There are several ways in which reliving is likely to facilitate elaboration of the trauma memory: 1) it links previously unconnected parts of the traumatic experience, thus giving context 2) reliving facilitates the retrieval of elements of the trauma memory that are difficult for the patient to access otherwise 3) patients may link information they received after the trauma to correct their impression and thoughts during the trauma so that the event poses less current threat to the self 4) reliving facilitates the discrimination between the ‘then’ and ‘now’.

In vivo exposure

In vivo exposure to avoided reminders of the trauma is a powerful way of helping patients to emotionally accept that the traumatic event is in the past.

Identifying triggers of intrusive memories and emotions

Discrimination for stimuli that occurred around the time of the trauma and those encountered currently can be enhanced by direct interventions aiming at better discrimination. Patients may benefit from training in spotting triggers of intrusive memories or negative affect and physical sensations related to the trauma Once triggers are identified, detailed discussion of the similarities and differences between the present and past context can be used to facilitate discrimination.

Imagery techniques

Imagery techniques are useful in elaborating and changing the meaning of the trauma memory.