Trauma exposure is exceedingly prevalent; an estimated 70% of individuals will experience at least one traumatic event in their lives (Kessler et al., 2017; U.S. Department of Veterans Affairs, 2019). While most individuals are resilient in response to trauma, lifetime prevalence rates indicate a substantial subset (5-9%) go on to develop post-traumatic stress disorder (PTSD: American Psychiatric Association, 2013; Cloitre et al., 2019; Kessler et al., 2017; Kilpatrick et al., 2013; Thompson et al., 2018; Wisco et al., 2014; Wu et al., 2013). A vast body of literature has shown that repeated trauma exposure (Delahanty, 2006; Delahanty et al., 2003; Jakob et al., 2017; Karam et al., 2014; Kessler et al., 2018; Lee & Park, 2018; Milligan-Saville et al., 2018; Ozer et al., 2003; Shalev et al., 2019; Wu et al., 2013), and previous trauma history significantly increases risk of PTSD development (Jakob et al., 2017; R C Kessler et al., 2018; Reger et al., 2019; Shalev et al., 2019). Therefore, reliable and accurate measurement of prior trauma history is important in research of trauma-related outcomes in order to assess its specific contributions to PTSD vulnerability.

The Life Events Checklist (LEC) is a widely used self-report measure of prior trauma history that was designed to accompany the Clinician Administered PTSD Scale (CAPS) in aiding PTSD diagnosis (Gray et al., 2004; Weathers et al., 2013). The LEC consists of 17 questions about various traumatic events a person may have experienced, each asked in reference to the degree of (i.e., proximity to) exposure (i.e. experienced, witnessed, learned about). The LEC has demonstrated good test-retest reliability (item-level Kappa’s > 0.50) and strong convergence of total scores with validated PTSD symptom severity measures (Pearson r’s ranging from 0.34-0.48) including the Traumatic Life Events Questionnaire (TLEQ; Kubany et al., 2000), PTSD Checklist (PCL; Blevins et al., 2015), and CAPS (Gray et al., 2004; Weathers et al., 2013). In non-clinical samples, the LEC also has moderate test-retest reliability, with events that were directly experienced being the most reliably reported (Pugach et al., 2020).

By sorting traumatic events according to proximity, the LEC is able to capture a myriad of traumatic experiences that may have differential impacts on an individual (Benfer et al., 2018; Irish et al., 2008; Kelley et al., 2009; Keshet et al., 2019). However, the scoring protocol instructs all endorsed items across all exposure types to be summed together to generate a total score (Gray et al., 2004). This method of scoring does not account for the notion that proximity of exposure may carry different risk conferral for PTSD than others (Sareen, 2014). For example, sexual assault has been shown to be more traumatizing (i.e. greater PTSD symptom severity) than the sudden death of a loved one (Benfer et al., 2018; Kelley et al., 2009; Keshet et al., 2019). Although researchers have published manuscripts utilizing this total scoring method (Belleau et al., 2020; Chung et al., 2014; Heir et al., 2019; Letica-Crepulja et al., 2020; Weis et al., 2018; White et al., 2015), others have attempted to capture the notion that proximity to the trauma is an important consideration (e.g. Møller et al., 2020; Reger et al., 2019). The LEC can also be scored to “count” only the endorsed experienced items (e.g. Møller et al., 2020; Reger et al., 2019), if those events really do carry the greatest risk, though this approach has not been validated (Milligan-Saville et al., 2018). Furthermore, only considering the events directly experienced by an individual does not capture the trauma load of other forms of exposure assessed in the LEC.

We have framed the proposed method in the context of evidence suggesting that all trauma types, even events that are learned about, are important when assessing cumulative life trauma (Baker et al., 2020; Conrad et al., 2017; Sacchi et al., 2020) as well as the substantial evidence that direct proximity to (i.e., “experienced”) trauma bestows additional risk (Benfer et al., 2018; Kelley et al., 2009; Keshet et al., 2019; Milligan-Saville et al., 2018; Qi et al., 2016; Reger et al., 2019). Therefore, in order to harmoniously bridge these two conceptualizations and fully capture the utility of the LEC, the current report proposes an alternative scoring procedure for the LEC to measure prior trauma history. In two traumatically injured clinical samples, we evaluated whether a total weighted LEC score, according to proximity of trauma exposure, may better capture the relationship between previous trauma history and risk of PTSD compared to the unweighted total and experienced events only score.

For sample characteristics see Table 1 and Supplemental Tables 1 and 2. There were no significant gender differences in the three LEC scoring methods for either sample. There were no gender differences in total CAPS in the iSTAR sample (p > 0.05) though females in the STAR 1.0 sample had significantly greater CAPS symptom severity (t(100) = −2.02, p = 0.04). The sample from STAR 1.0 was significantly older than the sample in iSTAR, t(308) = 6.34, p < 0.01. While inclusion criteria were the same for both samples in terms of age (18-60), the STAR 1.0 sample tended to be older as there were sometimes competing health concerns resulting in their admittance to the hospital post-trauma. Age was not significantly related to CAPS symptom severity in the iSTAR sample, but in the STAR 1.0 sample, greater age was significantly related to greater CAPS symptom severity (t(171)= −3.60, p < 0.01).

There were no significant differences in the scores produced by the three LEC scoring methods between the two samples (Experienced: t(450) = 1.06, p = 0.28; Total: t(434) = 0.89, p = 0.37; Weighted: t(438) = 0.99, p = 0.31). In addition, both samples had comparable CAPS symptom severity scores at 6-months, t(325) = −0.10, p = 0.91.

First, LEC metrics were evaluated for reliability of measurement across both samples. Pairwise correlations demonstrated all three LEC measures were highly correlated with one another at baseline for both samples (all p < 0.01, Table 2).

Internal reliability results indicated experienced only scores demonstrated poor reliability for both samples (α < 0.67), while total scores demonstrated excellent reliability in both samples (α > 0.87), and weighted scores demonstrated good reliability in both samples (α > 0.83; Table 3; Hair, 2010).

To characterize the relationship of the three LEC scores with PTSD symptoms, all three LEC scoring methods were correlated with total CAPS symptom severity at 6-months. In the iSTAR sample, all three LEC scoring measures were highly correlated with CAPS symptom severity at 6-months (all p < 0.01). In the STAR 1.0 sample, experienced only scores at baseline were highly related to CAPS severity at 6-months (p < 0.01; Table 4).

Finally, to compare degree of correlation significance between LEC measures with CAPS severity, Hotelling’s t were calculated between all pairwise combinations of the LEC measures and the CAPS. In the iSTAR sample, there were no significant differences in correlation significances for any pairwise comparisons of LEC correlations with CAPS (all p > 0.50). In the STAR 1.0 sample, total versus weighted scores yielded a significant difference in correlation significance (p = 0.02) such that weighted scores had a statistically more significant relationship with the CAPS than total scores. Even though the experienced LEC measure was the lone scoring method related to CAPS in the STAR 1.0 sample, the relative difference between total and weighted scores was greater than experienced versus total (p= 0.09) or experienced versus weighted scores (p= 0.21).

While exposure to previous trauma has been shown as a significant risk factor in PTSD development (Jakob et al., 2017; Kessler et al., 2018; Reger et al., 2019; Shalev et al., 2019), different scoring methods have been utilized for the Life Event Checklist (LEC), a widely used trauma exposure instrument. Therefore, the current study evaluated the reliability and validity of various LEC scoring methods and proposed a new method wherein exposure to trauma was weighted by the proximity to exposure (i.e., experienced, witnessed, learned about). In two independent traumatically-injured civilian samples, we demonstrated good reliability and validity of a novel weighted scoring method and compared it to the total and experienced only scoring methods.

Unsurprisingly, results of the reliability analysis show the weighted score is significantly and highly correlated with the standard total score and the experienced only score. The weighted score also had very good internal reliability (α > 0.83). In addition, the weighted score had better internal reliability than the experienced only score (α > 0.59), though not as high of reliability as the standard total score (α > 0.87). Of particular interest within the current study, was the validity of the weighted LEC score in predicting PTSD symptom severity. In both samples, the experienced events only score was significantly predictive of PTSD symptom severity assessed with CAPS-5 at follow-up. However, the weighted score only showed robust predictive utility with PTSD symptom severity in one sample (iSTAR). The difference in predictive utility may stem from the different natures of the samples (see limitations).

Although the experienced only scores were most predictive of PTSD symptom severity, experienced only events had the worst reliability of the three measures. While this result underscores the well-documented significance of experienced traumatic events in risk of PTSD (Benfer et al., 2018; Irish et al., 2008; Kelley et al., 2009; Keshet et al., 2019; Milligan-Saville et al., 2018; Qi et al., 2016; Reger et al., 2019), it may not be the most reliable measure of trauma history; however, poor reliability could simply be due to the fewer number of items in the experienced score compared to total and weighted scores (Cronbach, 1951). Weak internal reliability but strong correlation with PTSD symptoms may also suggest some of the experienced events in particular were stronger predictors of PTSD than other experienced events. However, the nature of this relationship cannot be further evaluated due to the lack of event context recorded by the LEC (see limitations).

Moreover, while the standard LEC total demonstrated the highest reliability, it does not capture the degree to which various trauma exposure types may confer PTSD risk (Benfer et al., 2018; Irish et al., 2008; Kelley et al., 2009; Keshet et al., 2019). Therefore, we have suggested an alternative method to capture the importance of experienced events in a reliable way. The weighted score emphasizes experienced events while still including the other forms of trauma exposure, and in the current study had excellent reliability over experienced events only. Of note, the weighted score is supported by research indicating that proximity of the traumatic event is a factor that confers differential risk of PTSD. However, it is important to note that is not the only factor, or perhaps even most important factor, by which risk of PTSD is conferred. Subjective interpretations and perceptions of trauma vary by individuals and are important when assessing trauma outcomes (Brasel et al., 2010; Geiger et al., 2011; Keshet et al., 2019). The utilization of the standard total score is also based on an assumption, that all traumatic events, regardless of proximity, impact an individual in the same way or to the same degree. Choice of a score (weighted versus standard) should be considered within the context of LEC administration, whether as a direct predictor of PTSD or as a covariate in other analyses, and with the consideration of how the underlying assumptions behind each scoring method may apply to a particular sample or research question.

A notable aspect of the current study is the inclusion of racially diverse samples. In both the iSTAR and STAR 1.0 samples 67% and 54% of participants, respectively, identified as a race other than White. While previous work has shown trauma, PTSD, and culture intersect in complex ways (Alegría et al., 2013; Chemtob, 1996; Ungar, 2013), in the U.S., prevalence of PTSD is one of many health disparities that varies by racial and ethnic groups. More specifically, several studies have demonstrated higher rates and conditional risk for PTSD for Black and African Americans when compared to Hispanics, Latinx, Asians, and Whites (Alegría et al., 2013; Roberts et al., 2011). Despite this empirical evidence, reliability of PTSD risk assessments, like the LEC, have not been appropriately evaluated in a diverse sample (Gray et al., 2004; Weathers et al., 2013). Thus, the current study adds to the literature by presenting reliability indices of various scoring methods for the LEC while utilizing a more representative trauma sample and encourages future work to include cultural considerations in study designs.