Why Don’t All Trauma Survivors Develop Post-traumatic Stress Disorder?
A Multi-method Exploration of Resilience.
LITERATURE REVIEW
Author: Vivien Le Fort
Supervisors: Dr Anke Karl and Dr Janet Smithson
Nominated journal: Journal of Traumatic Stress
This manuscript has been submitted in partial fulfilment of a Doctoral degree in Clinical
Psychology.
Word count: 3975 (excluding references).
Contents
1. Abstract………………………………………..………………………………….………3
2. Review
2.1 Background………………………..…………………………………………….4
2.2 Conceptual and definitional issues....…………………………………………...5
2.3 Post-trauma pathways……………..…………………………………………….6
2.4 Theoretical understanding of PTSD development..……………………………..7
2.5 Review of variables associated with the resilience pathway……………………8
2.5.i Pre-trauma vulnerability factors……………………………………….9
2.5.ii Peri-trauma vulnerability factors……………………………………..11
2.5.iii Post-trauma vulnerability factors…………………………………….12
2.6 Methodological review and recommendations………………………………….13
2.7 Gaps in existing knowledge……………………………………………...……...16
2.8 Future directions…………………………………………………………………16
3. References…………………………………………………………………………….…..18
Why Don’t All Trauma Survivors Develop PTSD?
A Multi-method Exploration of Resilience: Literature Review.
Abstract
Many individuals who experience trauma do not go on to develop post-traumatic
stress disorder (e.g., Johnson & Thompsen, 2008). Longitudinal studies have demonstrated
that resilience is the most common of several potential trajectories of trauma response
(Bonnano, 2004; Bonnano, Westphal & Mancini, 2011; Norris, Tracy & Galea, 2009),
challenging the assumption that resilience reflects extraordinary coping ability (Bonnano,
2004). Interest has grown in identifying the variables that distinguish resilient individuals
from those who develop psychopathology (Elwood, Hahn, Olatunji & Williams, 2009) with
calls for further research to focus on this issue (e.g. Schaubroeck, Peng, Riolli & Spain,
2011), which has clear clinical relevance in terms of PTSD treatment implications. Emotion
regulation has emerged as a potentially important variable in distinguishing resilient
individuals from those who develop PTSD but new methodological approaches are required
to develop understanding of this complex topic.
Keywords: Post-traumatic stress disorder, resilience, coping, trauma, emotion regulation.
Review
Background
Many individuals will experience a traumatic event at some point during their lifetime
which might be serious enough to invoke the feelings of horror, fear and helplessness that
fulfil Diagnostic and Statistical Manual criteria for PTSD development (DSM-IV-R;
American Psychological Association, 2000). PTSD is a highly disabling condition (Elsesser,
Sartory & Tackenburg, 2005), characterised by three symptom clusters: intrusive
recollections, avoidance and numbing, and hyper-arousal symptoms such as hyper-vigilance
(APA, 2000). However, the majority of trauma-exposed individuals do not develop PTSD,
even following prolonged and extreme stressors such as war trauma and torture (Johnson &
Thompsen, 2008).
The purpose of this review is to explore the factors which influence whether
individuals who experience a traumatic event recover or develop PTSD. The review of the
literature was conducted using the search databases BioMed Central, EBSCO E-Journals,
JSTOR, ScienceDirect and PsychArticles. Due to the size of the literature and the focus on
an up to date review articles published before 2000 were not included. The key words “posttraumatic stress”, “posttraumatic stress”, “PTSD”, “resilience” and “trauma recovery” were
used for searches of the empirical literature. Literature such as conference papers,
unpublished manuscripts and non-peer reviewed articles were excluded from the review.
This review briefly outlines conceptual and definitional issues associated with the
concepts of PTSD and resilience and considers the main post-trauma pathways followed by
survivors. Current theoretical understanding of PTSD development and research into the
variables that influence whether a trauma exposed individual is likely to develop PTSD or
follow a different response trajectory are reviewed. It is argued that the complexity of both
PTSD and resilience as constructs requires the utilisation of a greater range of methodologies
in order to develop understanding of the relationship between these ideas and identify
possible recommendations for those who experience trauma to strengthen resilience and
reduce the likelihood of PTSD development.
Conceptual and Definitional Issues
Difficulties with the concept of trauma resilience include the large and heterogeneous
population to which the term applies and problems with definitions of both PTSD and
resilience. Davidson, Stein, Shalev and Yehuda (2004) found that up to 90% of an adult
sample in the United States had been exposed to a traumatic event that would meet the
required standard for potential PTSD development (APA, 2000) and McNally (2003) referred
to the problem of bracket creep, the diagnostic changes in the different versions of the DSM.
Some authors (e.g. Pole, 2007) have questioned whether contradictory findings in parts of the
PTSD literature were caused by sampling differences due to the wider criteria in DSM-IV
(APA, 2000) compared to previous versions.
PTSD can occur following single or multiple traumatic events. Differences between
PTSD sufferers in terms of trauma exposure have led to suggestions that the PTSD concept
be divided into sub-types. Davidson et al. (2004), for example, found that the most extreme
adverse effects of traumatic events were associated with complex on-going traumas that
occurred in childhood and associated this with the proposed sub-type of complex PTSD, in
which exposure at an early age to chronic traumatic interpersonal violence results in more
chronic and disabling PTSD with higher levels of dissociation. This illustrates the dilemma
in PTSD research between developing understanding of a highly heterogeneous group or
seeking to identify and research potential sub-types within the PTSD concept.
PTSD is more clearly understood than its counterpart, resilience. Although Bonnano
(2004) argued that resilience is a normal response to trauma, rather than reflecting
extraordinary coping ability, it has traditionally been conceptualised from a pathogenic or
salutogenic approach (Almedom & Glandon, 2007). Many different definitions of resilience
have been utilised (Lee, Sudom & McCreary, 2011), with suggestions that definitions of
resilience should include more than just the absence of pathology (e.g., Bonnano, Galea,
Bucciarelli & Vhahov, 2007; Almedom & Glandon, 2007) and some authors proposing
mathematically originated definitions (Norris, Tracy & Galea, 2009), such as the time
required for a system to return to equilibrium (Bodin & Wiman, 2004).
Almedom and Glandon (2007) argued that resilience is a complex term describing a
dynamic state. In this regard it has similarities with PTSD, which can also be considered
dynamic and complex given the oscillation between hypo-arousal and hyper-arousal
symptoms and the different time trajectories over which the disorder can develop and rescind.
Similar issues are found with the related concept of post-traumatic growth, with PatHorenczyk and Brom (2007) noting how this term has been used in the literature to refer to
an attitude or cognition, behaviour, form of coping, outcome or even process of meaningmaking. A critical review by Zoellner and Maercker (2006) highlighted similar concerns and
concluded that the concept of post-traumatic growth as a coping outcome provided a
worthwhile new perspective, despite the current inconclusive and contradictory findings in
the literature, due to the potential clinical benefit of moving from deficit-oriented approaches
to understanding trauma recovery.
Post-trauma Pathways
Longitudinal analyses have identified several post-trauma trajectories, the most
common being an experience of minimal PTSD symptomatology either initially or over time,
a pathway described as resilience (Bonnano, 2004; Bonnano et al., 2007; Bonnano, Westphal
& Mancini, 2011) or resistance (Norris et al., 2009). Other post-trauma trajectories involve
some PTSD symptomatology, either chronically, initially but with recovery, or delayed onset
symptomatology (Bonnano, 2004).
Theoretical Understanding of PTSD Development
There is not currently a universally accepted theory of PTSD (Elwood et al., 2009).
PTSD was originally explained in terms of stress models (Lanius, Frewen, Vermetten &
Yehuda, 2010), with the traumatic event thought to result in a profound generalised effect on
the individual, for example increasing baseline levels of stress hormones and physiological
arousal. Kennell-Tacket (2009) gave the example that people who have experienced trauma
have higher rates of a variety of illnesses than the general population, and explained this in
terms of trauma priming the inflammatory response system, resulting in a more rapid
response to subsequent life stressors.
Alternatively, diathesis-stress models (e.g. Bowman & Yehuda, 2004; McKeever &
Huff, 2003) propose an underlying pathogenic mechanism, which may be a disorder-general
or specific risk or vulnerability factor, which remains dormant until sufficient stress results in
activation. Once activated, the mechanism influences functioning across the system and may
lead to the development of a disorder. However, such models do not explain why removal of
the stressor would not over time result in a reduction of stress-related symptoms (Lanius et
al., 2010).
Other models have focussed on the importance of cognitive responses. Foa and
colleagues (Foa & Kozak, 1986; Foa, Steketee & Rothbaum, 1989) developed the fear
conditioning model in which individuals either habituate to or avoid the anxiety associated
with fearful memories. Avoidance prevents habituation and paradoxically increases reexperiencing and reinforces fear. Emotional processing, defined as the modification of
memory structures which underlie emotion in this instance fear, is indicated by physiological
activation and habituation.
Ehlers and Clarke (2000) also emphasised the role of cognitive processes in the
development of PTSD, suggesting that individuals with PTSD experience a sense of current
serious threat from their traumatic memory as a consequence of both negative appraisals and
difficulties with encoding the trauma into autobiographical memory.
Finally an emotional dysregulation mode has been proposed by Lanius et al. (2010),
who suggested that fear is not the prevailing emotion in PTSD but only one of several
components implicated in an emotional dysregulation system. They proposed two potential
pathways: firstly, that emotional dysregulation is the outcome of stress sensitization and that
individuals alternate between emotional over- and under-modulation in an attempt to manage
unwanted emotional experiences. Secondly, they built on the stress-diathesis model and
suggested that for individuals with childhood onset trauma, these experiences act as a distal
vulnerability factor by causing inadequate neurodevelopment of the emotional and arousal
regulatory systems.
Current models of PTSD are therefore able to account for the complexity of the
condition with regards to the presence of hypo- and hyper-arousal symptoms. However they
make different predictions regarding the importance of variables that might indicate
vulnerability to PTSD following trauma. The cognitive models emphasise appraisal and
subsequent avoidance behaviours as developing and maintaining factors, which could be
influenced by pre-trauma variables. The stress models and subsequent redevelopments
indicate a greater role for pre-disposing factors that might influence the point at which stress
sensitization occurs or vulnerability factors are activated.
Review of Variables Associated with the Resilience Pathway
Researchers have examined the risk and vulnerability variables that influence
resilience. Many variables have been identified, operating at the pre, peri and post trauma
time periods, but the combined explanatory power of these variables is often low (Elwood et
al., 2009). However, Bonnano et al. (2011) argued that there may be multiple, independent
predictors of resilient outcomes, with various risk and resilience, stable and fluctuating
factors combining in a cumulative or additive manner.
Pre-trauma Vulnerability Factors
Childhood trauma. Nnamdi Pole and colleagues found that exposure to childhood
trauma can alter psychobiological systems involved in subsequent threat appraisal and
reactivity. Pole et al. (2006) found that childhood trauma was positively associated with
longer lasting changes in the psychobiological processes that mediate response to
environmental threats and increase sensitivity to threat. Early stresses may establish effects
that cascade through later developments and limit the organism’s flexibility in adapting to
new, challenging situations. The results imply that life-threatening experiences occurring
during childhood can influence the developing nervous system.
Attachment. Resilience has been positively correlated with secure attachment and
negatively correlated with preoccupied and fearful attachments (Simeon, Cunilla, Yehuda et
al., 2007). These researchers found that childhood trauma was positively associated with
cortisol and that higher cortisol levels predicted increased resilience. They concluded that
low baseline cortisol levels may be a risk factor predisposing individuals to develop
psychopathology, such as PTSD, following trauma exposure.
Personality. Lee, Whitehead and Dubiniecki (2010) examined personality and health
outcomes following trauma and identified a variety of positively associated traits. It was
unclear whether the personality variables affected outcome directly or were mediated by a
third variable, such as extraversion may increase the likelihood of having more positive social
interactions. This idea has been tentatively supported by Pole et al.’s (2006) survey of
resilient retired police officers, who identified sharing work-related matters with friends and
family as one of their most important characteristics.
Schaubroeck, Peng, Riolli and Spain. (2011) developed a meta-concept called positive
psychological capital, comprising self-efficacy, optimism, hope and ego-resilience. They
suggested that the impact of this variable on resilience was based on the cognitive appraisals
made of the level of threat posed by the stressful event. Mancini and Bonano (2006) also
found evidence for increased resilience following the 9/11 terrorist attacks being positively
associated with ego-resilience and hardiness. They suggested that the best predictor of
resilience two years following the attacks was flexibility in emotion regulation, measured as
the ability to engage in either suppression or expression when instructed to do so.
Demographic variables. Although many studies have focused on individual level
variables (Bonnano et al., 2007), demographic variables have been associated with resilience
following trauma, although findings suggest that the relationship is not straightforward. For
example, Elwood et al. (2009) found that female gender predicted lower resilience. However,
Lily et al. (2009) explored why gender differences have not typically been found in military
and police studies and found that female police officers experienced significantly less peritraumatic dissociation and fewer PTSD symptoms than female civilians, suggesting that
gender differences are not explained solely by biological sex.
Other demographic variables positively associated with lower resilience include lower
socioeconomic status, lower education, lower intelligence and belonging to a black or ethnic
minority group (Elwood et al., 2009; Bonnano et al., 2007) although this last point was not
supported by Mancini and Bonnano (2006) who found that Asian ethnicity was positively
associated with higher resilience, as was being married and more highly educated. They
suggest that ethnic cultural variation remains an enormous and important outstanding
question in resilience theory.
Physiological arousal. Many studies have found heightened physiological arousal to
trauma related stimuli for participants with PTSD compared to healthy controls (see Pole,
2007, for meta-analytic review). Prospective studies have suggested that heightened
physiological reactivity may however be a pre-existing vulnerability factor for PTSD.
Guthrie and Bryant (2003) found that pre-trauma skin conductance response to startle stimuli
in firefighters predicted post-traumatic stress severity. However, Orr et al. (2003) found that
combat veterans with PTSD showed a different physiological response to acoustic startle than
their twins, concluding that the heightened response of the veterans was an acquired sign of
PTSD and not a vulnerability factor.
Peri-trauma Vulnerability Factors
Psychophysiological responsivity. Although it is unclear whether heightened
physiological reactivity is a pre-existing vulnerability factor for PTSD development, the
finding that individuals with PTSD have heightened psychophysiological reactions to trauma
related stimuli has been reported almost uniformly (Orr & Roth, 2000). Pole’s (2007) metaanalysis found that PTSD was positively associated with higher resting arousal, larger
responses to startling sounds, larger responses to standardised trauma cues, and larger
responses to ideographic trauma cues.
Psychophysiological regulation. The most robust effect in Pole’s (2007) metaanalysis was, however, a measure of a regulatory process rather than response, specifically
skin conductance habituation slope to startling sounds. Therefore the key feature of PTSD
may be the failure to show typical psychophysiological recovery or adaptation. Pole (2007)
concluded that, whilst heightened arousal and reactivity had led most investigators to
emphasise abnormalities in the sympathetic nervous system and other biological systems
involved in reacting to stress, PTSD may more reliably be characterised by abnormalities in
the parasympathetic nervous system and other biological systems involved in recovering
from stress. Jovanovic and Ressler (2010) commented that an inability to control response to
stressors may be a vulnerability factor for PTSD development or an acquired trait of the
illness.
Peri-traumatic dissociation. Dissociation during trauma exposure has been found to
be a strong predictor of PTSD development (Elwood et al., 2009), with significance reported
in both prospective and retrospective studies (Lily et al., 2010). Elsesser, Freyth, Lohrmann
and Sartory (2008) suggested that this may reflect a compensatory mechanism to limit
distress in response to marked arousal, or may be an evolutionary response similar to freezing
when confronted with inescapable danger.
Cognitive appraisal. Given that trauma severity has been found to be a strong
predictor of PTSD (Elwood et al., 2009), it is possible that an individual’s appraisal of the
severity of their traumatic experience might influence their recovery. Schaubroeck et al.
(2011) proposed that individuals may vary in the extent to which they perceived a stressful
event in more or less threatening terms. Elwood et al. (2009) suggested that various schemas
about the self, others and world may function as cognitive vulnerabilities, which could
operate at the pre-, peri- or post-traumatic level. An example of the impact of cognitive
appraisal of self on PTSD development is provided by Luszczynska, Benight and Cieslek
(2000)’s systematic review of evidence for a relationship between self-efficacy beliefs and
health outcomes following trauma, where beliefs about one’s ability to deal with adversity
was a powerful predictor of post-traumatic recovery.
Post-trauma Vulnerability Factors
Social support. Lack of social support has been found to be a strong predictor of
poor resilience (Elwood et al, 2009). Bovier, Chamot and Pergerer (2004) explained this
effect as an interaction between intrapersonal and interpersonal variables, for example social
support increasing self-esteem whilst higher self-esteem increases confidence to access social
support opportunities. The influence of social support can also be conceptualised as a
resource within Hobfall’s (1989) conservation of resources theory, with Almedom and
Gandon (2007) describing social support as a generalised resistance resource. It may also
underlie Mancini and Bonnano’s (2006) finding that being married was a predictor of
resilience in survivors of the 9/11 attacks. Pole et al.’s (2006) finding that retired police
officers described sharing work-related matters with family and friends and avoiding
distancing coping strategies as key to their resilience suggests that the ways in which social
support is utilised may further refine understanding of this variable. An interpretative
phenomenological analysis of interviews with individuals who had lived in disadvantaged
and risky circumstances by Stanley (2011) also identified relationships as a resilience theme.
Further life stress. Bonnano et al. (2007) found that amount of life stress predicted
resiliency, a finding replicated by Elwood et al (2009). However, this contradicts Lily et al.’s
(2009) finding that female police officers reported significantly more exposure to traumatic
events than female civilians but less severe PTSD symptoms. This suggests that there may be
a third variable mediating this relationship, which Lily et al. (2009) suggested might be
maladaptive emotion suppression.
Therefore although a range of variables significantly positively associated with
resilience have been identified, the operation and potential mediators of these remain unclear.
There is some disagreement about the extent to which some variables predict post-trauma
difficulties or occur as a consequence of them or whether the trauma exacerbates an existing
vulnerability. This overview suggests that closer examination of how the variables operate is
necessary, requiring a review of potential methodologies to achieve this aim.
Methodological Review and Recommendations
Sampling. There are three main populations to recruit from for PTSD and resilience
research: PTSD sufferers, trauma survivors and people likely to experience trauma as a
consequence of a high risk occupation. Each strategy has associated considerations. PTSD is
a highly co-morbid condition, with Davidson et al. (2004) finding that more than 80% of
sufferers also experienced at least one other lifetime disorder, most commonly depression and
substance misuse. It is also a condition which is often treated with medication. This has
implications for participant exclusion criteria. Pole (2007) argued that excluding medicated
individuals can reduce outcome generalizability by yielding samples with uncharacteristically
low symptom severity.
Davidson et al. (2004) noted that many people with PTSD fail to seek help, or present
with somatic symptoms, possibly reflecting the avoidance element of PTSD. Hoge et al.
(2004) found that a prevailing stigma still existed in returning veterans about perceptions of
weakness should PTSD symptomatology be admitted. Therefore, a sampling bias may exist
in that only some PTSD sufferers are known to services and accessed for research.
Trauma survivors often pose the difficulty that a diverse nature of trauma has been
experienced, both in terms of severity and frequency. Researchers have attempted to reduce
this variance by working with survivors of the same, large-scale trauma, such as the 9/11
terrorist attacks (e.g. Mancini & Bonnano, 2006) or hurricane disaster (Norris et al., 2001).
Researchers often include a measure of social desirability in these studies to identify whether
participants have amended their trauma experiences. Norris et al. (2009) noted that disaster
survivors are more representative of the general population than the highly selected samples
often used in research.
Finally, some prospective study designs have examined healthy participants who are
likely to be exposed to trauma as a consequence of a high risk occupation, such as the
military. However, Pole (2007) argued that it is then unclear to what extent results can be
generalised to the wider population, given that characteristics of the individuals who choose
such careers may distinguish them in other ways to other groups.
Design. Within both PTSD and resilience literatures, cross-sectional and
retrospective self-report designs have been dominant. There are fewer longitudinal studies
(although see Barel et al.’s (2010) meta-analysis of studies of holocaust survivors).
A major gap in both literatures is the absence of qualitative research. Given the focus
on the process of resilience phenomenological methods might be highly appropriate.
Although some researchers have begun to use qualitative methods to explore people’s
experiences of trauma (e.g. Stanley, 2011), these studies have been in the minority.
Measures. Measurement has been limited by a heavy reliance on self-report and
retrospective measurement of vulnerability. Bonnano et al. (2011) criticised resilience
measures, questioning what they actually measure and opposing reliance on such measures in
the absence of assessment of outcomes. Almedom and Glandon (2007) have argued that
resilience cannot be measured in isolation from its context and have suggested that measures
should be accompanied by qualitative investigation and analysis.
Cross-sectional designs have measured physiological reaction to stressors such as
sudden loud noises (e.g. Guthrie & Bryant, 2003) or traumatic stories (e.g. Frewen & Lanius,
2010), pictures (e.g. Elsesser, Tackenburg & Sartory, 2004), or videos (e.g. Carleton,
Sikorski & Asmundson, 2010). These stimuli fall far short of the life-threatening events
described in definitions of PTSD and so there is an assumption that the individual will react
in a similar way in terms of psychophysiological response or concepts such as peri-traumatic
dissociation.
Although various psychophysiological measures have been used to assess responses
to stressors, heart rate habituation has not been widely used, despite Pole’s (2007) conclusion
that heart rate was a consistently significant and theoretically relevant indicator, and that
habituation rather than immediate response might be the key mechanism in PTSD. HetzelRiggin (2010) suggested that psychophysiological measurement is important because it is
objective and allows direct assessment of reactivity and arousal.
Recommendations for methodological research in this area therefore include a wide
and inclusive sampling strategy, designs which allow for individual differences to be
explored and measured without reliance on inadequate rating scales or solely self-report data,
the inclusion of qualitative methods, and the examination of actual resilience following
trauma rather than simply reactions to stressors.
Gaps in Existing Knowledge
Despite the identification of numerous variables which have statistically significant
association with resilience, the combined explanatory power is low (Elwood et al., 2009).
Theoretical models of PTSD have focussed primarily on the aetiology of the disorder,
identifying that vulnerability factors and individual differences are important, but with
limited explanation of how these might integrate to predict outcome following trauma
exposure.
The primary gap is therefore a detailed understanding of how specific variables
operate, individually or together, both in the laboratory and with real life trauma experiences.
Future Directions
Some researchers have recommended that future studies focus on specific elements of
the PTSD syndrome in order to begin to untangle these issues. Pole (2007) recommended
that habituation, reflecting how quickly an organism can regulate its response to repeated
aversive stimuli, be further explored. Given the findings that heart rate had a generally
stronger effect than other startle responses and that heart rate can reflect SNS and PNS
influence, the measurement of heart rate habituation to stimuli may be a fruitful area for
further research.
It is not known whether trauma resilient individuals are particularly competent at
managing their emotional responses, as suggested by Mancini and Bonnano’s (2006) findings
with survivors of the New York terrorist attacks. This hypothesis could be explored in a
heart rate habituation laboratory paradigm. Such a study would be especially useful if it
examined a general population rather than exclusively male military veterans, who have
dominated the literature to date and consequently reduced generalizability of results (Pole,
2007).
Several researchers have identified the need for multi-modal data given the complex
nature of PTSD. Elwood et al. (2009) called for the use of combinations of self-report,
behavioural and physiological data and Pole (2007) suggested the inclusion of self-report or
observer measures corresponding to the psychophysiological symptom under investigation.
Researchers could then examine how well and for whom psychophysiological measures
correspond with other measures. Schaubroeck et al. (2011) suggested that further research
should study how people respond during the period they are exposed to traumatic events.
Multi-method research may therefore be a useful step forward in this field.
Interpretative phenomenological analysis (IPA; Smith, 2004) has been used recently with
topics related to PTSD and resilience, such as the experience of being a family member of a
veteran with PTSD (Ray & Vanstone, 2009), exploration of young offenders’ responses to
traumatic experiences (Paton, Crouch & Camic, 2009) and examination of the experiences of
people living in risky and disadvantaged circumstances (Stanley, 2011). Given the focus on
developing a rich understanding of the experience of an individual who has undergone a
major life event, IPA would appear a particularly appropriate method for the exploration of
trauma-resilient participants’ coping strategies.
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