Memory processes

Cognitive models of PTSDs hypothesise that re-experiencing occurs because of how memories of traumatic experiences are encoded, organised and retrieved (Brewin Reference Brewin, Dalgleish and Joseph1996, Reference Brewin2014; Ehlers Reference Ehlers and Clark2000; Hyland 2023). Table 2 outlines key theoretical and phenomenological differences between the memories that characterise PTSDs and ordinary episodic memories of extremely psychologically threatening experiences. According to the dual representation theory of PTSD (Brewin Reference Brewin, Dalgleish and Joseph1996, Reference Brewin, Gregory and Lipton2010), the storage of episodic memories relating to any experience (positive or negative) involves two separate memory and representation systems: (a) sensation-based representations (S-reps) encode multisensory/perceptual (primarily image-based) information, supported primarily by subcortical structures and areas of the brain directly involved in perception; and (b) contextually bound representations (C-reps) encode cognitive and spatial information, including the current autobiographical self, and involve higher-order cognitive activity. Ordinary, functional encoding (of positive memories, negative memories and processed PTSD memories) in episodic memory involves the creation of C-reps and S-reps, with connections between the two. In contrast, re-experiencing results from the creation of an S-rep (perceptual memory) without the usual association to a corresponding C-rep.

TABLE 2 Theoretical and phenomenological differences between post-traumatic stress disorder (PTSD) memories and ordinary episodic memories of extremely threatening experiences

S-rep, sensation-based representations; C-rep, contextually bound representations.

The dual representation theory (Brewin Reference Brewin, Dalgleish and Joseph1996, Reference Brewin, Gregory and Lipton2010, Reference Brewin2014) hypothesises that reliving arises if, during extreme stress and horror, an individual's brain prioritised encoding survival-related perceptual information and action over higher-order cognitive activity. Increased encoding into S-reps and reduced encoding into C-reps and the connections between S-reps and C-reps result in multisensory information not being encoded with enough contextual information, with the result that it can only be recalled involuntarily when automatically triggered by trauma reminders. This leads to the brain responding as though past experiences are happening again in the present, producing intense reliving, with associated emotional and physiological reactions. These issues mean that individuals can retrieve C-reps of experiences when they want to deliberately think or communicate about them, but these are fragmented and disorganised.

Reliving can be thought of as the brain trying to make sense of experiences: re-presenting information for more detailed processing when the danger has passed. ‘Processing’ traumatic experiences (with or without professional support) involves holding intrusive trauma memories in focal attention, strengthening C-reps and the connections between C-reps and S-reps such that multisensory information is given a temporal and spatial context and fits with the current autobiographical self and core beliefs.

Problematic meanings

The second mechanism hypothesised by cognitive models to be central to explaining the development and maintenance of PTSDs is the appraisals people have regarding traumatic experiences and their sequelae and what these mean for the self (Ehlers Reference Ehlers and Clark2000; Hyland 2023). PTSDs are characterised by threatening, excessively negative or distorted – and therefore unhelpful – appraisals/beliefs about traumatic experiences and/or their consequences. The memory and identity theory proposes that ICD-11 PTSD and CPTSD are distinguished by the types of negative identities/beliefs present, with ICD-11 PTSD involving identities centred on experiencing the self as powerless and unsafe, whereas ICD-11 CPTSD additionally involves identities related to experiencing the self as worthless/inferior, betrayed/abandoned, alienated, fragmented and/or non-existent (Hyland 2023).

Maladaptive coping

Cognitive models of PTSDs hypothesise that the manner in which individuals cope is another psychological mechanism that is central to explaining the development and maintenance of PTSDs (Ehlers Reference Ehlers and Clark2000; Hyland 2023). Individuals use a range of cognitive and behavioural avoidance strategies to cope with a sense of current threat and PTSD symptoms because these experiences are too distressing and/or cannot be understood within the person's current core beliefs/identity. Unfortunately, these management strategies inadvertently maintain PTSDs by directly producing PTSD symptoms, preventing change in negative appraisals of trauma and/or its sequelae, and preventing change in the nature of the trauma memory (Ehlers Reference Ehlers and Clark2000).

Individual differences in vulnerability

Cognitive models of PTSDs recognise individual differences in vulnerability to developing PTSDs. Ehlers and Clark's (Reference Ehlers and Clark2000) model provides the most detailed discussion of the range of ways in which background factors are likely to influence cognitive processing during traumatic events, the nature of trauma memories, appraisals of trauma/its sequelae and the strategies used to control perceived threat/PTSD symptoms.

The clinical interview in more detail

After outlining the individual's ethical rights and setting up the assessment, expert witnesses are advised to begin assessments with open questions and free recall, as these are the most effective means of eliciting large amounts of uncontaminated information. Briefly asking individuals about current home circumstances and education/employment, for example, helps establish rapport. Individuals can then be asked to tell the story of the index event(s) (describe what happened); if distress or potential PTSD symptoms (e.g. avoidance) are observed, reflective questions might be asked about what it is like to think and talk about these experiences. These initial sources of information help establish rapport and swiftly elicit a wealth of clinical information pertinent to the expert's aims, informing preliminary hypotheses about possible and likely diagnoses and psychological formulations, and identifying potential inconsistencies and information that will need assessing in more detail.

Continuing to use primarily open (non-leading) questions, the expert can then move to more specific assessment of an individual's mental health over time using cued invitations (e.g. ‘Tell me more about X’), direct questions (concerning who, what, when, where, how, why), and a mixture of open and closed questions, aiming to elicit further details and clarify unclear and contradictory information. The diagnostic criteria for any mental health problems being reported (e.g. PTSDs) need to be comprehensively assessed.

Expert witnesses may assess pre-, peri- and post-index-event variables, and how cognitions, behaviour and functioning have changed from before to after experiences. A theory-informed assessment of PTSDs – which considers memory characteristics, problematic meanings and maladaptive coping – is recommended and further informs: (a) why a particular individual developed PTSDs when they did; (b) understanding maintaining factors and treatment targets; (c) differential diagnosis; and (d) attributing mental health problems and functional impairment/disability to specific events when an individual has experienced multiple traumas. The nature of reliving (i.e. what intrusive memories, flashbacks and nightmares are about) and the appraisals people have about traumatic experiences and/or their consequences help in understanding the differential and cumulative impact of different experiences of trauma and adversity.

As the clinical interview continues, the focus shifts from sensitivity (identifying relevant mental health difficulties) to specificity (accurate diagnosis and psychological formulation). If two or more diagnoses might plausibly describe an individual's index event-related mental health problems, further information-gathering may be needed. The assessment continues until uncertainty about the most accurate diagnostic impression and psychological formulation are minimised.

Administering psychometric instruments

Expert witnesses may collect psychometric information about an individual's PTSDs and other mental health problems to corroborate and extend information gathered during clinical interview. Measures usefully quantify the presence and severity of symptoms. Some example PTSD measures are provided in Table 4. There are advantages and disadvantages to different approaches: semi-structured interviews ensure systematic, comprehensive assessment of diagnostic criteria and provide the highest inter-rater reliability, but are more time-consuming to administer, whereas questionnaires collect large amounts of clinical information swiftly and easily but may be more susceptible to bias than interviews. Some professionals fear that collecting self-report information ahead of a clinical interview may influence clinical interview responses; I have not observed this myself and I am not aware of any evidence for or against this hypothesis.

TABLE 4 Some example measures of post-traumatic stress disorder (PTSD) and complex PTSD (CPTSD)

When PTSDs are being considered as a legal defence

PTSDs may be considered as a legal defence to argue for temporary diminished responsibility, loss of capacity, insanity or duress, or as a mitigating factor in sentencing. In addition to the considerations discussed above, the expert witness's role in such circumstances is to carefully assess how PTSD symptoms relate to specific (criminal) behaviours. For example, a flashback could plausibly cause a temporary, abrupt behaviour change beyond the person's volition (‘automatism’; Kopelman 2022); an individual's perceptions, decision-making and capacity for self-control may have been influenced by trauma-related beliefs/expectations (e.g. heightened perceptions of threat); irritability and aggression may have made an individual easily provoked; negligent behaviour may have occurred due to chronic insomnia. In cases of memory loss specifically for an offence, it is important to determine whether memory loss was partial or complete and to ask about the onset of amnesia and the return of normal, continuing memories and any ‘islets’ of memory in between (Commane Reference Commane and Kopelman2022).

Further comments about differential diagnosis

It is beyond the scope of this article to review the numerous possible and likely alternative diagnoses to PTSDs but some general comments can be made. First, since PTSDs are a disorder of memory, an intimate understanding of trauma memory characteristics (Table 2) is critical to differential diagnosis. Second, meticulous interviewing and thinking are required to form and clearly describe accurate clinical impressions. Third, accurate differential diagnosis is obviously dependent on fluent knowledge of the diagnostic criteria for a range of diagnoses. A common error involves mistaking the reliving symptoms that specifically characterise PTSDs with (a) ‘thinking about’ trauma only when reminded; (b) non-intrusive memories of traumatic experiences; (c) intrusive thoughts, images and memories (which are transdiagnostic); (d) blaming oneself or others; or (e) trauma-related preoccupation, worry or rumination (which involves repetitive ‘coulda/woulda/shoulda’ thoughts and focusing on how bad one's life is or could have been because of one or more experiences). Another common mistake involves not delineating different mental health problems/disorders and whether and how they interact. The most obvious way to accurately differentially diagnose involves carefully assessing and describing the nature of trauma-related mental health responses and how different diagnostic criteria are or are not met.

Factors that may affect reliability

Broadly speaking, the evidence base indicates that memory is essentially reliable but malleable and subject to contamination under certain circumstances; that memory quantity and the richness of episodic detail decline as the retention period increases, although the details people do recall are pretty accurate across time; that it tends to be more difficult to recall thoughts and feelings than it is to recall events; that the reliability and accuracy of recollections cannot be easily verified by other people (including professionals) except by reference to other sources of information; and that susceptibility to false memories of childhood events appears more limited than has sometimes been suggested (Brewin 2011a, Reference Brewin and Belli2011b, Reference Brewin2014, Reference Brewin and Andrews2017a, 2019a, Reference Brewin, Andrews and Mickes2020; Wixted 2018; Commane Reference Commane and Kopelman2022; Baddeley Reference Baddeley, Brewin and Davies2023). Civil claims and repeated interviews about past distressing events invite individuals to reflect on past experiences, sometimes leading to re-interpretation of past events, potentially attaching to events a significance that they did not originally have. The phenomenological characteristics of PTSDs (Table 2) may affect perceptions of an individual's reliability.

Expert witnesses must critically consider the extent, nature, consistency and quality of the available evidence when diagnosing, formulating and caveating their professional opinions. When considering records and collateral information, it is important to remember that informant discrepancies are common (De Los Reyes Reference De Los Reyes, Augenstein and Wang2015) and perceptions of other people's difficulties and abilities vary greatly in accuracy, detail and degree of bias, depending on a range of factors. Corroborating information across varied sources, time and contexts helps overcome biases and weaknesses in any one information source. More generalised and caveated professional opinions about mental health difficulties and psychiatric diagnosis are appropriate for events that are more distant in time, when there is less available information and when the information available is of poorer quality or inconsistent. Highlighting inconsistencies, gaps and contradictions in the available evidence and discussing possible and likely reasons for these valuably informs the court, but expert witnesses must always stick to their role: it is for the court to make determinations on fact.

Trauma-focused psychological therapy

Trauma-focused psychological therapy (TFPT) is recommended as the first-line treatment for PTSDs in all populations in guidelines across the world. Large effect sizes and clinically meaningful symptom improvement are generally observed as a result of TFPT (Mavranezouli 2020a, 2020b). However, some individuals do not engage in TFPT (i.e. do not start therapy); a small number of individuals drop out (Simmons 2021); and a substantial number retain a PTSD diagnosis (Cusack Reference Cusack, Jonas and Forneris2016) or high levels of symptoms (Larsen 2019) at the end of TFPT. In my clinical experience, trauma processing is a one-way street such that PTSDs do not return if they have been fully processed – unless an individual's life circumstances change such that they once again no longer perceive they are post-trauma. Definitions of what constitutes ‘permanent’ PTSD or impairment differ (e.g. 5+ years’ duration) across contexts.

Trauma-focused psychological interventions – which involve elements of processing trauma memories and altering problematic trauma-related cognitions – are superior to non-trauma-focused interventions (Coventry Reference Coventry, Meader and Melton2020; Mavranezouli 2020a, 2020b). TFPT is typically delivered weekly, although it can be delivered more intensively (e.g. daily; Ehlers Reference Ehlers, Hackmann and Grey2014; Bongaerts Reference Bongaerts, Voorendonk and Van Minnen2022). Typically, 6–12 sessions are required for more straightforward presentations, but more sessions may be indicated (National Institute for Health and Care Excellence 2018). Almost all clinical trials conducted to test the effectiveness of TFPT have not distinguished between ICD-11 PTSD and CPTSD – suggesting that TFPT is effective for both diagnoses. Meta-analyses indicate that TFPT causes reductions in comorbid mental health problems and is effective for individuals thought to have experienced ‘complex trauma’ (Coventry Reference Coventry, Meader and Melton2020); is equally effective in relation to PTSDs arising after single and multiple traumatic events (Hoppen 2023, 2024); and is effective in reducing ICD-11 CPTSD DSO symptoms (Banz Reference Banz, Stefanovic and von Boeselager2022).

Some authors suggest that a safety and stabilisation ‘phase’ is always requiredFootnote ^d before trauma-focused intervention (i.e. before targeting the mechanisms thought to be central to the maintenance of PTSDs; Ehlers Reference Ehlers and Clark2000; Kangaslampi 2022; Hyland 2023). There is great variability among clinicians and academics as to what constitutes ‘stabilisation’, which interventions are offered as part of a stabilisation phase, under what circumstances/for whom stabilisation is needed and whether to ever proceed beyond stabilisation work. The limited evidence available indicates that interventions with a dedicated stabilisation ‘phase’ neither improve outcomes nor reduce drop out (Oprel 2021; van vliet 2021); critics argue that this approach is an unnecessary use of clinical time and delays change (de Jongh Reference de Jongh, Resick and Zoellner2016). Anecdotally, therapists sometimes use a stabilisation phase because of their anxiety about engaging in exposure work (Waller 2009, 2016), meaning it could potentially be conceptualised as a therapist therapy-interfering behaviour.

Overall, most clinicians and academics seem to agree that TFPT should be individualised, formulation-driven and involve multiple components; should address the problems that most concern the individual experiencing PTSD (Cloitre Reference Cloitre2015); and should be delivered by a suitably trained, regulated and qualified professional who is receiving appropriate clinical supervision. Given limited evidence that a phase-based approach is superior, and uncertainty about whether a stabilisation phase is needed at all, it seems best and most ethical to seek to ameliorate PTSDs by targeting the mechanisms theorised to be central to their maintenance, rather than to help people to live with their symptoms.

Remote assessment and therapy

Working remotely became popular during the COVID-19 pandemic. It confers several advantages, including reducing geographical barriers and travel time and costs, overcoming logistical challenges in attending appointments (e.g. due to caring responsibilities or an impairing health condition) and increased convenience. The available evidence suggests that remote psychological and psychometric assessment of PTSDs and remote psychological therapy are generally comparable to working face to face in terms of effectiveness, safety and acceptability for clinicians and patients (Batastini Reference Batastini, King and Morgan2016, Reference Batastini, Paprzycki and Jones2021; Olthuis 2016; Wild 2020; Bongaerts Reference Bongaerts, Voorendonk and van Minnen2021, Reference Bongaerts, Voorendonk and Van Minnen2022). The appropriateness of remote assessments must be considered on a case-by-case basis, in collaboration with involved parties, prioritising clinical need, ethical rights and choice, and accounting for any contraindications (e.g. poor digital access/awareness, cognitive difficulties, auditory or visual impairments, severe mental health problems, high levels of risk, young age).

Accessing therapy

Many people experiencing PTSDs wait years or decades before disclosing past experiences and seeking professional help. Several barriers potentially limit access to TFPT, including lack of confidence in treatment effectiveness; fear of PTSD symptoms worsening; perceived stigma regarding psychological therapy; practical barriers (e.g. transportation, treatment availability); and long waiting times (Smith 2020).

The right time

Expert witnesses are encouraged to explicitly discuss alternative treatment options with the individuals they are assessing so that realistic recommendations and prognostic predictions can be made. It is each person's ethical right to choose whether and when they want to engage in TFPT. Although TFPT may seem indicated, it may not be the right time for an individual to engage in therapy. Crown Prosecution Service (2022) guidance on pre-trial therapy emphasises prioritising the well-being of the victim, giving informed choice regarding treatment, and not delaying therapy if it would be in the victim's best interest; the recommendations may be different outside of England and Wales. However, it can be difficult or impossible to ‘put the trauma in the past’ if current or future situational factors mean that an individual does not perceive that they are post-trauma (e.g. preoccupation with an asylum claim outcome, ongoing interviews and legal process, ongoing trauma exposure or threat).

Suicidal thoughts and psychoactive substance use are common in individuals experiencing PTSDs (Luciano 2022; Hien 2023). These, insomnia, severe distress and severe flashbacks and dissociation, are sometimes perceived as reasons to delay treatment (Murray 2022). However, these factors are not necessarily contraindications for TFPT. The relationship between PTSDs and other difficulties needs to be carefully assessed and considered. Ameliorating PTSDs often addresses other difficulties (Hien 2023; Luciano 2022; Murray 2022). PTSDs and comorbid substance use can be treated effectively by TFPT (Hien 2023). However, during TFPT individuals must not be too emotionally numbed to bring distressing trauma memories to mind; thus, an individual may be using substances in general, but should not do so for hours or days before each therapy session if this seems to be impacting progress.