Challenges in the retrospective assessment of trauma: comparing a checklist approach to a single item trauma experience screening question

Compared to people without a trauma history, trauma survivors are at higher risk of many problems including depression, substance abuse, suicidal behaviour, physical illnesses and poverty [1–3]. One of the possible consequences of trauma is posttraumatic stress disorder (PTSD), an often severe and disabling condition with a lifetime prevalence in the general population of up to 9 % [4–11]. Unlike other mental illnesses, the diagnosis of PTSD requires not only symptoms but also a cause; that is, the occurrence of a trauma event which posed an actual or threat of death, serious injury or sexual violence in one of the following ways: directly experiencing, witnessing, learning that it occurred to close family member/friend or repeated exposure to aversive details of trauma events [12]. Epidemiological studies of PTSD typically rely on a subjective assessment by the participant and/or researcher as to whether a particular event was sufficiently severe to justify being a “trauma”. However, in practice this may be difficult to determine. Recall bias [13, 14], an individual’s subjective interpretation of events [15] and type of the event itself [8] may strongly influence whether an individual who has experienced an event sees it as traumatic.

Although exposure to trauma events is widespread, affecting 21–89 % of the population in their lifetime [7–11, 16], only a minority will go on to develop a mental disorder. Experiencing an unpleasant event as a trauma is not an objective process. The trauma experience is filtered through cognitive processes relating to the appraisal of an event which may be perceived by some, but not all, individuals as a severe threat [15]. Cognitive appraisal is also an important part of the stress response mechanism [17]. Theoretical models have posited the role of cognitive appraisals as mediators in the development and persistence of trauma-related psychopathology [18]. Among survivors of traumas, negative appraisals of the meaning of the trauma appear to account for symptoms of depression and posttraumatic stress beyond objective measures like frequency and severity of trauma [19].

One of the factors influencing retrospective accounts of life events is current mental health status. Cohort studies of people who were exposed to the same traumatic event have reported that the retrospective report of the trauma was affected by current mental health. Severity of PTSD symptoms at follow-up are associated with an increase in retrospective accounts of the frequency and severity of exposure to trauma events. Those doing better, with a lower severity of symptoms at follow-up reported the event as less disturbing than they previously had [20–22]. A similar association was also observed with worsening self-rated perception of health and endorsement of new trauma experience at follow-up [23].

Research into factors influencing the recollection of trauma events has so far mainly focused on highly selective samples, such as individuals who suffered childhood sexual abuse [24–26] or combat-related trauma [20, 22]. Most of these studies assessed the consistency of reports of traumatic events on repeated assessments over a period of time. However, to the best of our knowledge, the consistency of reports obtained using different methods to assess trauma experience has never been done in a community sample.

In the present study, participants were asked about trauma experiences twice within the same interview. First, we used a checklist of life events and participants were asked whether they had experienced each of the events on the checklist. With this approach all events were treated as equivalent. Second, participants were asked as part of a PTSD checklist whether they had ever experienced an event that either put them or someone close to them at risk of serious harm or death (i.e. a “trauma” in the meaning of the PTSD questionnaire). This approach allowed respondents to appraise the experience of the trauma event and give a subjective judgement to the experience [27]. The aims of the present study are to assess how these two different responses correspond, and to examine which factors are associated with reporting a trauma experience in those who previously reported a specific event on the life event checklist. We hypothesise that individuals with a current common mental disorder will be more likely to report a trauma experience than those without.

Exposure to trauma in South East London is considerably higher than in other studies of inner city populations in Europe (21 % in Munich and 28 % in Zurich) [7, 9]. In this study the majority (72.1 %) of the sample reported at least one item from the checklist of life events that qualified as trauma [12]. However, less than half (46.0 %) of those who reported a trauma item on the checklist reported a trauma experience they perceived put them or close others at risk of serious harm. Unlike the checklist which allows participants to endorse events without a rating of severity or the threat that the event posed, participants are required to exercise their judgement of the severity of a threat on the trauma experience screening question.

Women were more likely to report a trauma experience. This could be due to a gender difference in post trauma cognitions (meaning-making) which was suggested by previous studies as a possible explanation for gender differences in PTSD [19]. It could also be due to a gender difference in the type of trauma experienced, with women experiencing more interpersonal trauma than men [19]. However, a post hoc analysis revealed that the number reporting interpersonal trauma was similar between women (70.9 % (95 % CI 67.2–74.5) and men (71.2 % (95 % CI 67.4–75.0)) and there was no gender difference in reporting trauma experience by type of life event (the results are available on request from the authors). The higher likelihood for women to endorse traumatic experiences could partly explain the observed higher prevalence of PTSD among women reported in several studies, including the previous report from the same population whereby men were more likely to report a trauma event, but women were more likely to experience symptoms of PTSD [11]. This supports the argument that the high prevalence of PTSD in women may not be due to an increased overall risk of trauma, but due to a greater vulnerability to the effects of trauma events [4, 8, 16, 35, 36].

We did not observe the hypothesised difference in reporting a trauma experience between those with current common mental disorder and those without (after adjustment). The fact that the association between the experience of life event before the age of 16 years, cumulative life event and reporting a trauma experience did not diminish after accounting for mental disorder, suggests that they are directly linked and not mediated by current mental health state. Although several follow up studies have reported an association between current mental health state and how people remember their traumatic experience, these studies did not consider the effects of cumulative and childhood trauma which are more likely in individuals with mental disorder [20–22].

We observed a strong association between cumulative life events captured on a checklist and reporting a trauma experience. The negative appraisal of an event may not only depend on the experience of an individual event, but also on previous exposure to trauma [18]. Greater trauma exposure relates to more negative cognitions about oneself and the world which predicts how individuals interpret and make sense of their experience [19]. This may provide one explanation for the association observed in previous studies between previous exposure to trauma event and posttraumatic stress disorder (PTSD) resulting from subsequent trauma [35, 36].

Our findings highlight an association between exposure to stressful life events during childhood and reporting a trauma experience. This could be due to the severity of the events included in the childhood stressful life events questions, or that victims of child abuse are more likely to experience trauma as an adult [37], or alternatively that they are more likely to perceive subsequent stressful events as a traumatic experience [18]. Reporting stressful events before the age of 16 years may also be a marker for an individual’s early life environment, e.g. neglect, which may also play a role in emotional development and later responses to trauma. This is consistent with findings from other studies in the general population sample and in combat veterans that reported those who experienced childhood trauma had a higher risk of PTSD in adulthood from subsequent trauma [5, 35, 38].

In the PTSD literature a wide range of events such as spousal infidelity [6], marital disruption [39], miscarriage [40] and childbirth [41] have also been reported to be associated with the onset of PTSD even though they may not all meet the DSM criteria for a trauma. In the current study we also found a small proportion (4 %) of participants who reported a trauma experience even though they did not report any of the events from the life event checklist which met this criterion. Whilst this may be partly explained by the limitation of the life event checklist which is not exhaustive, it is possible that they had experienced other life events which would not meet the criteria for trauma. On the other hand, many individuals do not develop PTSD despite the experience of extreme life threatening trauma like torture under captivity as prisoner of war [42]. Some studies have reported the importance of subjective measures of perceived threat as a better predictor of PTSD symptoms than objective measures of danger, including in studies of torture survivors [43], burn victims [44], and accident survivors [45]. These studies showed that the appraisal of the threat was a key determinant of whether an event triggers PTSD or not and the stress response also depends on whether the stressor is appraised as threatening or not [17]. This could be translated to other mental and physical health consequences of trauma. Events that are appraised as threatening are more strongly associated with high demands and lead to biological changes like increased peripheral vascular resistance [46] and higher reactive levels of cortisol [47–51].

The trauma experience question in this study was taken from DSM-IV where the stressor is defined as an event that has been experienced or witnessed. In the DSM-5 criteria the definition of the stressor has been broadened to include learning that the traumatic event(s) occurred to a close family member or friend (with the actual or threatened death being either violent or accidental) and experiencing repeated or extreme exposure to aversive details of the traumatic event. Whilst we were unable to assess the DSM-5 criteria in the current study, future research may find that this change in wording influences responses on the trauma screening question.

Our study demonstrates that gender, early life trauma and greater accumulation of life events may influence an individual’s judgement concerning the severity of threat posed by an event. This subjective processes contributes to individual differences in the screening of trauma and to discrepancies between participants’ reports of traumatic life events on a checklist, compared to when using a DSM event screening tool. Our findings did not support our hypothesis that current symptoms of CMD would account for differences in reporting of traumatic experiences. However, our results suggest that epidemiological approaches to assess PTSD which require participants to make subjective judgements in defining trauma, may capture individual differences in this perception process, for example by gender and previous trauma experience.

Subjective interpretation of a trauma is crucial in relation to the subsequent psychobiological response to that trauma. Understanding the mechanisms underlying the connection between the cognitive appraisal process as it relates to the factors identified in this study (gender, multiple trauma and early life trauma), would help to build more effective models of intervention addressing the mental and physical health consequences of trauma.