Psychological theories of posttraumatic stress disorder.
Brewin, C.R., & Holmes, E.A. (2003)
Clinical Psychology Review, 23, 339-376

Psychological processes and PTSD

Memory and PTSD

In PTSD, there are a number of changes in memory functioning that are comparable with depressed patients: 1) a bias toward enhanced recall of trauma-related material 2) difficulties in retrieving autobiographical memories of specific incidents.

Specific changes in memory of PTSD are: 1) a contradictory patterns of recall related to the traumatic material itself. High levels of emotions are in some studies associated with more vivid and long-lasting memories, but in others with vague memories, lacking in detail and error prone. PTSD is described as characterized by both high-frequency, distressing, intrusive memories and by amnesia for the details of the event. 2) the reliving of memories, or flashbacks to the trauma. Flashbacks are dominated by sensory detail. These images and sensations are typically disjointed and fragmentary. Reliving is reflected in a distortion in the sense of time, such that the traumatic event seems to be happening in the present rather than belonging in the past. Reliving episodes are triggered involuntarily by specific reminders that relate in some way to the circumstances of the trauma.

Flashbacks are a distinctive feature of PTSD.

Individual differences in working memory capacity appear to be related to the ability to prevent unwanted material from intruding and negatively affecting task performance.

Attention and PTSD

Research does not provide evidence that the effects of an attentional bias are unique to PTSD.

Dissociation and PTSD

Dissociation are any kind of temporary breakdown in what we think of as the relatively continuous, interrelated processes of perceiving the world around us, remembering the past, or having a single identify that links our past with our future.

Mild dissociative reactions are common under stress.

Dissociative symptoms most commonly encountered in trauma include: emotional numbing, derealisation, depersonalisation, out-of-body experiences. They are related to the severity of the trauma, fear of death, and feeling helpless.

It has been suggested that such reactions reflect a defensive response related to freezing in animals.

When these symptoms occur in the course of a traumatic experience, they are referred to as ‘peri-traumatic dissociation’.

The presence of dissociative symptoms occurring after rather than during trauma is not consistently associated with risk for later PTSD.

Cognitive-affective reactions and PTSD

A requirement of the PTSD diagnosis according to the DSM-IV, is to experience intense fear, helplessness, or horror at the time of the trauma.

There is a strong relationship between each of the specific reactions in victims of violent crime and the risk of PTSD.

Mental defeat is the perceived loss of all autonomy, a state of giving up in one’s mind all efforts to retain one’s identity as a human being with a will of one’s own. It goes beyond helplessness in attacking the person’s very identity.

Some emotions are the direct result of outcomes, others depend on an element of cognitive appraisal. Posttrauma, cognitive appraisal of the cause of, responsibility for, and future implications of the trauma will provide numerous opportunities to generate negative emotions.

Feelings of guilt, shame, sadness, betrayal, humiliation, and anger frequently accompany PTSD.

High levels of anger (specifically with others) predict a slower recovery from PTSD. Shame is a predictor of how PTSD symptoms develop over time.

Beliefs and PTSD

The subjective perception of threat is an influential predictor of distress and failure to respond to treatment. Traumatic events shatter people’s basic beliefs and assumptions.

A general increase in negative beliefs about the self, others, and the world has been found in trauma victims with PTSD.

Trauma has the potential to destroy trust and lead to the belief in victims that they have been let down or betrayed.

High levels of anger with others reported by PTSD patients are consistent with a loss of belief in the good intentions of other people.

PTSD is associated with the belief that trauma has brought about a negative and permanent change in the self and in the likelihood of achieving life goals.

Negative interpretations of symptoms predicted a slower recovery from PTSD. Negative beliefs do not have to occur during the trauma itself, but may represent the outcome of a separate appraisal process that only begins after the danger is past.

If beliefs occurred peri-traumatically, they could form part of the re-experienced trauma memory and thus be triggered by reminders of the trauma.

Cognitive coping strategies and PTSD

Attempts to suppress unwanted thoughts are usually doomed to failure. Afterwards, the thoughts return even more strongly.

Avoidance and thought suppression are related to a slower recovery from PTSD.

Coping strategies associated with greater risk of PTSD include: rumination and increased use of safety behaviours.

Social support and PTSD

A negative social environment is a good indicator of PTSD symptomatology. Negative appraisal of others’ support attempts predicts PTSD.

Negative social support is a stronger predictor for PTSD in women.

Early theories

Stress response theory

Horowitz argued that when faced with trauma, people’s initial response is to outcry at the realisation of the trauma. A second response is to try to assimilate the new trauma information with prior knowledge. At this point, many individuals experience a period of information overload during which they are unable to match their thoughts and memories of the trauma with the way that they represented meaning before the trauma. In response to this tension, psychological defence mechanisms are brought into play to avoid memories of the trauma pace the extent to which it is recalled. The fundamental psychological need to reconcile new and old information means that trauma memories will actively break into consciousness in the form of intrusions, flashbacks, and nightmares. These consciously experienced trauma memories provide the individuals with an opportunity to try to reconcile them with pretrauma representations.

According to Horowitz, two opposing processes are at work: 1) one to defend the individual by the suppression of trauma information 2) one to promote the working through of the traumatic material by bringing it to mind.

The individual oscillates between avoidance and intrusions of the trauma. This allows the traumatic information to be worked through, and as this happens, the intensity of each phase decreases. Longer term structures in memory representing the self or future goals can be adjusted so that they are consistent with the new data, at which point, the trauma processing is considered to be completed. Failure to process the trauma information is proposed to lead to persistent posttraumatic reactions as the information remains in active memory and continues to intrude and be avoided.

Areas not treated in this theory are: the difference between flashbacks and ordinary memories, individual variations in trauma response, peri-traumatic reactions, the role of environmental factors and how to distinguish remission of symptoms due to recovery from remission due to avoidance.

Theory of shattered assumptions

Three common assumptions that are regarded most significant in influencing response to trauma are 1) the world is benevolent, other people are in general well-disposed toward us, 2) the world is meaningful, there are reliable rules and principles that enable us to predict which behaviours will produce which kind of outcome 3) the self is worthy, we ourselves are personally good, moral, and well-meaning.

A traumatic experience has the potential to shatter deeply held and probably unexamined assumptions about how we believe the world and ourselves to be.

Updating of assumptions can take place spontaneously through the re-experiencing cycle described by Horowitz. It can also be made to occur deliberately by reflecting on the trauma.

Research has found that other assumptions may be more fundamental. For people to act in the world, they must have a set of beliefs that 1) the self is sufficiently competent to act 2) the world is sufficiently predictable 3) the world provides sufficient satisfaction of needs.

Traumatic incidents are highly unpredictable and unpleasant and produce feelings of intense helplessness, thereby challenging these beliefs. In some cases, this produces intense conflict and feelings of unreality.

According to the theory of shattered assumptions, people with the most positive experiences in life, who should therefore hold the most positive assumptions, should be the ones most affected by traumatic events. But, the opposite is the case.

Conditioning theory

An initial phase of fear acquisition through classical conditioning results in neutral stimuli present in the traumatic situation acquiring fear-eliciting properties through their association with the unconditioned stimulus. A wide variety of associated stimuli would acquire the ability to arouse fear through the processes of stimulus generalisation and higher order conditioning. Extinction would fail to occur if the person attempted to distract themselves or block out the memories, rendering the exposure incomplete. Avoidance of the conditioned stimuli would be reinforced by a reduction in fear, leading to the maintenance of PTSD.

People with PTSD develop conditioned responses more readily to aversive events in general, and these are harder to extinguish.

This approach does not clearly distinguish the etiology of PTSD from that of other anxiety disorders.

Information-processing theories

Central to information-processing theories is the idea that there is something special about the way the traumatic event is represented in memory and that if it is not processes in an appropriate way, psychopathology will result. It emphasizes the need for information about the event to be integrated within the wider memory system. The difficulty in achieving this is attributed to the characteristics of the trauma memory.

Lang proposed that frightening events were represented within memory as interconnections between nodes in an associative network. A fear memory consisted of interconnections between different nodes representing three types of propositional information 1) stimulus information about the traumatic event 2) information about the person’s emotional and physiological response to the event 3) meaning information, primarily about the degree of threat. Cognition and affect were integrated within an overall response program designed to rapidly escape or avoid danger.

Lang suggested that patients with anxiety disorders have unusually coherent and stable fear memories that are easily activated by stimulus elements, that may be ambiguous but bear some resemblance to the contents of the memory. When the fear network is activated, the person experiences the same physiological reactions and tends to make meaning judgments that accord to the original memory.  

What distinguishes PTSD from other anxiety disorders is that the traumatic event is of monumental significance and violates formerly held basic concepts of safety. A traumatic event leads to a kind of representation in memory that is different from one created in everyday experience. Fear networks in PTSD are characterized by 1) particularly strong response elements. 2) the overturning of basic assumptions about safety means that there will be a large number of environmental cues that cause the network to be activated. 3) The network has a low threshold of activation.

For information in the fear network to be integrated with the rest of a person’s memories, these strong associations would have to be weakened. The strength of the interconnections within the fear memory would have to be reduced so that other non-threatening memories could also be activated. In order to do this, the fear network needs to be activated, and modified by incorporating information that is incompatible with it.

PTSD reactions tend to persist when achieving exposure of sufficient length in all the elements in the fear network is difficult. Under these circumstances, only some associations are weakened.

Anxious apprehension model

Cognitive factors that occur after the trauma produce a feedback cycle of anxious apprehension. Patients with PTSD focus their attention upon and are hypervigilant for information about ‘emotional alarms’ and associated stimuli. False alarms occur subsequently in the absence of danger.

In PTSD, the focus of people’s anxious apprehension is on cognitive and physiological cues from the time of the actual trauma as they wish to avoid distress generated by alarms. The learned alarms generate hyperarousal symptoms, which through their association to cues present at the time of the trauma, result in a negative feedback loop ensuring successive re-experiencing symptoms. To prevent triggering of alarms, the person will tend to avoid emotional interoceptive information.

Recent theories

Emotional processing theory

The network theory has been elaborated. Individuals with more rigid pre-trauma views would be more vulnerable to PTSD. These could be rigid positive views about the self and the world, which would be contradicted, or rigid negative views which would be confirmed.

Negative appraisals of responses and behaviours could exacerbate perceptions of incompetence. These might relate to 1) events that took place at the time of the trauma 2) symptoms that developed afterwards 3) disruptions in daily activities 4) responses of others.

Beliefs that were present before, during and after the trauma could interact to reinforce the critical negative schema’s involving incompetence and danger that underlie chronic PTSD.

A number of mechanisms is thought to be involved in exposure treatment 1) repeated reliving should promote the habituation of fear. Reducing the level of fear associated with other elements in the trauma memory as well as countering the belief that such anxiety is permanent 2) it prevents avoidance of the trauma memory being negative reinforced 3) rehearsing trauma memory in a therapeutic environment incorporates safety information into the trauma memory 4) the trauma can be better discriminated from other potentially threatening events and seen as a specific case rather than one among many examples 5) exposure offers the possibility to experience the self as showing mastery and courage in the face of challenge 6) by reflecting on events in detail, patients may reject previous negative evaluations as being inconsistent with the evidence 7) the severity of the event frequently disrupts the cognitive processes of attention and memory at the time of the trauma and produces dissociative states. This leads to the formation of a disjointed and fragmented fear structure. Repeated reliving generates a more organized memory record that is easier to integrate.

Empirical evidence

The treatment method associated with emotional processing theory, prolonged exposure, is well established as a highly effective treatment for PTSD.

Improvement is related to reductions in levels of fear between treatment sessions, but not to reductions in fear within sessions.

The prediction that higher levels of fragmentation and disorganisation in the trauma narrative are related to the occurrence of dissociative responses has received relatively consistent support.

There is little evidence that dissociation leads to trauma narratives that are shorter and more simplistic.

There is no consistent evidence that improvement in therapy is related to changes in the structure of trauma memories, the initial activation of fear, or to habituation.

A general problem with the associative memory network approach is that it cannot represent knowledge at levels of meaning beyond that of the word or sentence, whereas there is reason for thinking that the meaning of emotional events tends to be complex.

Dual representation theory

Pathological responses arise when trauma memories become dissociated form the ordinary memory system and that recovery involves transforming then into ordinary or narrative memories. Unclear is if ordinary memories of the traumatic event can exist alongside dissociated memories, and how one form of memory is transformed.

One way of understanding this is to posit that there are two (or more) memory systems and that trauma information is better represented in one system than in the other. Cognitive psychologists proposed that there is a separate perceptual memory system that records information that has received little, if any, conscious attention. Experiencing events with high levels of emotion or importance results in the storage of long-lasting, vivid traces.

Brewin’s version of dual representation theory, two memory systems continue to operate in parallel. One may take precedence over the other at different times. 1) Verbally assessable memory system (VAM), reflected by oral or written narrative memories of trauma. Trauma memory is here integrated in with other autobiographical memories. These can be deliberately retrieved as and when required. These are represented within a complete personal context comprising past, present and future. The amount of information they contain is restricted because they only record what has been consciously attended to. These include emotions that happened at the time and generated by retrospective cognitive appraisal. 2) Situationally accessible memory system (SAM), triggered involuntary by situational reminders of the trauma. Contains information that has been obtained from more extensive, lower level perceptual processing of the traumatic scene that were too briefly apprehended to receive much conscious attention and did not become recorded in the VAM system. SAM also stores information about the person’s bodily response. This results in flashback being more detailed and emotion-laden than ordinary memories. This does not use a verbal code, making it difficult to communicate to others. It does not necessarily interact with and get updated by other autobiographical knowledge. They can be difficult to control. Emotions that accompany SAM memories are restricted to primary emotions that were experienced during the trauma.

PTSD is a hybrid disorder that potentially incorporates two separate pathological processes 1) involving the resolution of negative beliefs and their accompanying emotions 2) involving the management of flashbacks.

Requirements to recovery are: 1) reduce negative emotions generated by cognitive appraisal of the trauma, by consciously reasserting perceived control, reattributing responsibility, and achieving an integration of the new information with pre-existing concepts and beliefs 2) to prevent the continued automatic reactivation of situationally accessible knowledge about the trauma.

It was suggested that this is brought about by creating new SAMs that block access to the original ones. These would consist of the original trauma images paired with states of reduced arousal and reduced negative affect brought about by habituation or by cognitive restructuring of the meaning and significance of the event.

Neuropsychology and dual representation theory

Brewin highlighted the importance of the amygdala in activating fear responses and the different pathways that could convey trauma information to the amygdala. 1) Pathways involving processing by the hippocampus would result in the laying down of integrated, coherent representations of conscious experience, located in temporal and spatial context. These would be available for deliberate recall 2) Memories formed by an alternative pathway would not be open to deliberate recall, or locatable in a broader temporal or spatial context. These would be accessed automatically by reminders similar to those recorded in the trauma memory

Prolonged tress inhibits the functioning of the functioning of the hippocampus. This tends to reverse the improvement in declarative memory. Functioning of the amygdala appears enhanced as stress increases.

Verbally accessible memories suggest a form of representation that is dependent on the hippocampus. Because temporal context is encoded, they are experienced as in the past. Situationally accessible memories, experienced as happening in the present, highly perceptual,, elicited automatically, suggest non-hippocampally processing.

The lack of temporal context has two consequences 1) when the memories are retrieved, they are re-experienced in the present 2) the representation of ongoing threat leads to attentional and memory biases.

When the trauma survivor deliberately focuses and maintains attention on the context of the flashbacks rather than trying to suppress them, information that is only present in the SAM becomes reencoded into the VAM, at which point the memories are assigned a spatial and temporal context. This has to be repeated because there may be a lot of extra information about the trauma that has to be transferred. Eventually, providing the person is now safe, detailed memories in the SAM system that signalled the continuing presence of danger are matched by detailed memories in the VAM system that locate the danger in the past. If the new VAM memories are accessed, inhibitory pathways form the prefrontal cortex prevent inappropriate amygdala activation and the return of fear.

Dual representation theory maintains that the original trauma memories are not altered in any way, but remain intact and may be vividly re-experienced again in the future if the person unexpectedly comes across very detailed and specific reminders. Recovery is seen in terms of introducing retrieval competition.

People are thought to have in memory multiple self-representations or identities that compete to be retrieved. These identities provide a series of high-level frameworks that summarize experience with the world and with close relationships, and within which specific thoughts, images, or impulses are organized.Negative cognitions related to the trauma often arise because the event has made it difficult to retrieve positive self-identities or has reactivated negative self-identities created by previous adversity. Modifying these negative cognitions may involve exploring the existence of alternative identities that have been experienced by the person with PTSD and tracing links between these identities and the experience of trauma.
Cognitive therapy enhances the retrievability of positive identities by making them more distinctive and by creating new associative links that enable them to be retrieved following the activation of negative thoughts or images. Old representations remain unchanged and remain their potential to be retrieved by the right combination of cues.

Empirical evidence

The claim of dual representation that intrusive trauma images are supported by a different memory system, one that is predominantly visual is supported.

This theory is not linked to a detailed outline of therapeutic procedure.

Ehlers and Clark’s cognitive model

Pathological response to trauma arise when individual process the traumatic information in a way that produces a sense of current threat (external as well as internal).Two major mechanisms produce this effect: 1) negative appraisals of the trauma or its sequelae 2) the nature of the trauma memory.

The different types of appraisal explain the variety of emotions reported by patients with PTSD.

Among the factors that increase the likelihood of negative appraisals are: 1) thought processes during the trauma. Mental defeat is a risk factor for such self-appraisals as being weak, ineffective, or unable to protect oneself 2) prior beliefs and experiences.

Memory of the traumatic event is poorly elaborated, not given a complete context in time and place, and inadequately integrated into the general database of autobiographical knowledge. This accounts for: 1) the difficulty of intentional recall 2) re-experiencing in the present 3) the lack of connection with other information 4) easy triggering by physically similar cues.

Strong S-S and S-R associations for traumatic material are formed which help the person to make predictions about future sources of danger. Retrieval from associative memory is cue-driven and unintentional, so that the person may be unaware of the triggers for re-experiencing. Strong associations result in perceptual priming

There are a number of peri-traumatic influences that operate at encoding. They affect the nature of trauma memory 1) the distinction between data-driven processing (focused on sensory impressions) and conceptual processing (focused on the meaning of the situation, organizing the information, and placing it into context). Conceptual processing facilitates integration of the trauma memory with the autobiographical database. Data-driven processing leads to strong perceptual priming and memory that is hard to retrieve intentionally 2) an inability to establish a self-referential perspective while experiencing the trauma 3) dissociation 4) emotional numbing 5) lack of cognitive capacity to evaluate aspects of the event accurately.

Maladaptive behavioural strategies and cognitive processing styles maintain the disorder. Among the behavioural strategies likely to cause PTSD to persist are: 1) active attempts at thought suppression 2) distraction 3) avoidance of trauma reminders 4) use of alcohol or medication to control anxiety 5) abandonment of normal activities 6) adaption of safety behaviours to prevent or minimize trauma-related negative outcomes.

Empirical evidence

There is good evidence in support of various aspects of the model.