Childhood adversity and ASD

This was the case in our study, where sexual abuse emerged as a significant predictor of ASD at 9–15 days post-blast, whereas emotional abuse predicted ASD at 21–27 days post-blast. This finding is notable because, to our knowledge, the relationship between childhood adversities and ASD has not been thoroughly investigated previously. For instance, the retrospective matched-cohort study by Wang et al, which utilised the Taiwan National Health Insurance database to identify participants with a history of childhood abuse by using the ICD codes, measured the rates of multiple psychiatric disorders, including PTSD and ASD, but treated them as a combined entity (ASD/PTSD) rather than two distinct disorders. ^{Reference Wang, Chung, Chang, Kao, Chu and Wang19} Nevertheless, childhood adversities were found to be strong predictors of ASD/PTSD, with an odds ratio of 3.27. Similarly, Maunder et al measured acute stress response to assess the link between childhood abuse/neglect, response to critical incidents and mental/physical symptoms in paramedics. Acute stress response, encompassing somatic, depressive and burnout symptoms, was measured over a 2-week period following critical incidents. Those with a history of childhood abuse/neglect showed heightened acute stress responses and higher depressive, physical and burnout scores. ^{Reference Maunder, Halpern, Schwartz and Gurevich20} Although this study did not assess ASD according to diagnostic criteria (as ours did), it demonstrated that individuals with a history of childhood trauma experience heightened stress symptoms following adulthood incidents.

Childhood adversity and proxy PTSD

As for the relationship between childhood adversities and proxy PTSD, our results pertaining to full threshold DSM-5 proxy PTSD are consistent with existing literature. However, no previous studies have, to our knowledge, examined the association between childhood adversity and subthreshold PTSD. This distinction is critical, as subthreshold diagnoses are associated with high distress, low quality of life and high comorbidities, yet are often overlooked in the full-threshold provisional diagnosis of PTSD. ^{Reference Jakupcak, Conybeare, Phelps, Hunt, Holmes and Felker28,Reference Cukor, Wyka, Jayasinghe and Difede29} For instance, McLaughlin et al conducted a large-scale study involving 27 017 participants from the World Mental Health Surveys, identifying childhood adversities associated with PTSD. Among 12 adversities assessed, including interpersonal loss, parental maladjustment and maltreatment, individuals reporting physical abuse, sexual abuse, neglect and parental psychopathology were nearly twice as likely to develop PTSD after subsequent trauma (odds ratio 1.8), with sexual abuse and neglect emerging as the strongest predictors. ^{Reference McLaughlin, Koenen, Bromet, Karam, Liu and Petukhova16} In our present study, emotional abuse was also consistently associated with full threshold DSM-5 proxy PTSD and subthreshold proxy PTSD even after accounting for age and gender. Similarly, Widom’s study investigated the association between childhood abuse and neglect and subsequent PTSD, accounting for various familial, individual and lifestyle factors. Through matching victims of substantiated abuse and neglect with non-abused and non-neglected individuals followed into adulthood, the analysis revealed that childhood neglect was associated with an odds ratio of 1.75, indicating an increased susceptibility to PTSD. ^{Reference Widom30}

Interestingly, Sullivan et al conducted a study on 89 psychiatric in-patients, aiming to explore the impact of various subtypes of childhood on the severity of the individual PTSD symptom clusters (cluster B: re-experiencing, cluster C: avoidance and cluster E: arousal). The study found that sexual abuse predicted the re-experiencing symptom with an odds ratio of 1.24, whereas emotional abuse was a much stronger predictor of all the symptom cluster (re-experiencing: 1.43; avoidance and numbing: 1.62; arousal: 1.54), as well as overall PTSD severity (odds ratio 1.59). ^{Reference Sullivan, Fehon, Andrés-Hyman, Lipschitz and Grilo31}

Childhood adversity as a predictor of proxy PTSD: the intermediary role of ASD

Expanding on the observations that childhood adversities are predictive of both ASD and proxy PTSD, a pertinent question arises: Can childhood adversities directly predict proxy PTSD, bypassing ASD altogether?

When examining the longitudinal trajectory of childhood adversities in relation to ASD (within the first month post-blast) and proxy PTSD (6–7 months post-blast), we observed that participants without ASD in the month following the blast were more likely to develop subthreshold proxy PTSD (‘proxy PTSD majority’) if they reported at least one childhood adversity. This pattern was consistent at both time frames (9–15 days and 21–27 days post-blast).

As this is the first investigation, to our knowledge, into the longitudinal impact of childhood adversities on future proxy PTSD onset, both with and without going through ASD, a comparison with existing literature cannot be done. However, as this constitutes a novelty, it is imperative to try to explain the findings as to why individuals with a childhood history did not exhibit ASD early on, but later developed subthreshold proxy PTSD 6 months post-blast. Interestingly, among participants who developed ASD, a childhood history did not increase the risk of proxy PTSD 6 months later.

One potential explanation is that early exposure to adversities may foster post-traumatic growth, that is, positive psychological changes following exposure to trauma. ^{Reference Meyerson, Grant, Carter and Kilmer32} Introduced by Tedeschi and Calhoun, post-traumatic growth refer to emotional and cognitive processing of the trauma that leads to positive personality changes and coping mechanisms, ^{Reference Richard and Tedeschi33} thereby enhancing resilience. ^{Reference Bonanno and Mancini9} This was evident in Cabrera’s study on deployed troops, where exposure to ACE was found to decrease reactivity in the face of subsequent trauma exposure, specifically combat exposure. Soldiers with a history of ACE exhibited lower scores indicating fewer stress symptoms following combat, compared with those with no such history of childhood adversity. ^{Reference Cabrera, Hoge, Bliese, Castro and Messer34} Hence, it is plausible that some participants in our study developed resilience through post-traumatic growth, which protected them from ASD.

However, in the months following the blast, the situation in the country continued to deteriorate, with multiple collective stressors continuing to impact the participants, and this may have contributed to the onset of proxy PTSD. First of all, extensive media coverage displaying scenes of devastation may have retriggered memories of the blast, especially among healthcare workers at the most affected hospital in Beirut. They were simultaneously contending with infrastructure damage, a surge in COVID-19 cases and financial hardships following the economic crisis that began in 2020. The devaluation of the Lebanese currency (over 98%) and inflation exceeding 170% further amplified the stress. ³⁵

Such cumulative stressors may have contributed to the onset of proxy PTSD. Evidence suggests that repeated exposure to traumatic imagery, such as after the 9/11 attacks, leads to higher rates of PTSD among survivors. ^{Reference Ahern, Galea, Resnick, Kilpatrick, Bucuvalas and Gold36} Similarly, the repeated exposure to distressing media can serve as an additional indirect re-exposure, thereby causing increased psychological arousal and retriggering trauma responses. ³⁵ Furthermore, working in healthcare during the pandemic puts individuals at greater risk of developing PTSD. ^{Reference Canady37} Bryant’s 6-year longitudinal study on the trajectory of PTSD supports this. According to the sensitisation model of PTSD, individuals exposed to trauma may display exaggerated reactions to subsequent less severe stressors because of prior neural sensitisation. ^{Reference Bryant, Nickerson, Creamer, O’Donnell, Forbes and Galatzer-Levy38} This proposed analogy provides a plausible explanation for why individuals who initially showed no signs of ASD later developed PTSD. The initial resilience derived from childhood adversities may have protected participants from ASD, but was eventually overcome by cumulative post-blast subsequent stressors, ultimately resulting in proxy PTSD.

Regardless of the mechanism, our findings represent progress in disaster mental health research. In the immediate aftermath of large-scale disasters (being man-made or natural), disaster response workers utilise the Psychological First Aid – Field Operations Guide, developed by the National Child Traumatic Stress Network and the National Center for PTSD, to assess survivors and provide early intervention. ^{Reference Brymer, Layne, Pynoos, Ruzek, Steinberg and Vernberg39} Our findings are particularly relevant in this context, emphasising the importance of assessing childhood adversities during such interviews, especially among survivors who did not exhibit ASD. The likelihood of these individuals developing proxy PTSD later, even if they initially showed no proxy PTSD symptoms, is significant. Therefore, early intervention is vital as a preventive measure.

Strengths

This study offers novel insights with practical implications for improving public health responses in disaster settings. To our knowledge, it is the first study on the trajectory of childhood adversities leading to both full and subthreshold proxy PTSD, with and without the intermediary ASD diagnosis. Furthermore, it stands as the first robust study on the prediction of ASD diagnosis by childhood adversities. Furthermore, the study employed widely utilised assessment tools, which enhance the reliability and validity of the findings: the ASDS, which demonstrated strong internal consistency (Cronbach’s alpha of 0.94) in Karam et al’s study on the predictors of ASD; ^{Reference Karam, Saab, Al Barathie, Karam, Karam and Bryant40} and the PCL-5, which is also among the most commonly used instruments for proxy DSM-5 PTSD diagnosis, and has an excellent internal consistency of 0.92 in this sample. Similarly, two validation studies on the ASDS and PCL-5 in a Lebanese population were published that included criterion validity ^{Reference Karam, Al Barathie, Dimassi, Mascayano, Slim and Karam41} and construct validity. ^{Reference Al Barathie and Karam42}

Limitations

This study has several limitations that warrant consideration. First, the relatively wide confidence intervals observed in some models may be partly explained by the small sample size in specific subgroups, which reduces the precision of the estimates and warrants cautious interpretation of the findings. Nevertheless, our response rates across 21–27 days and 6–7 months post-blast were 38 and 41.88% respectively, which is considered a high response rate in online-based surveys. ^{Reference Wu, Zhao and Fils-Aime43} Unfortunately, the response rate 9–15 days post-blast could not be obtained because of the emergency nature of the situation immediately following the blast and during polymerase chain reaction testing (the data collection was face to face). Future research could mitigate this by employing larger multi-site recruitment strategies to ensure sufficient power. Second, both ASD and proxy PTSD (full threshold and subthreshold) were assessed using screening tools rather than structured clinical interviews, potentially affecting the accuracy of the diagnoses. Although it is imperative to note that during times of disaster, conducting structured clinical interviews may not be feasible and many researchers, including those in our study, resort to using valid screening tools as a pragmatic approach to assess these disorders. We acknowledge that the prevalence estimates derived from self-reported questionnaires can differ substantially from those obtained via interviews. This underscores that our reported numbers, although based on a validated and comprehensive instrument, may still overestimate or underestimate true prevalence of both full and subthreshold proxy PTSD and ASD. Third, only three out of the eight childhood adversities documented in the literature were evaluated in this study, limiting the comprehensiveness of our assessment. Future studies may adopt more inclusive instruments, such as the full ACEs questionnaire, to capture a broader range of adverse experiences. Additionally, participants self-reported their history of childhood adversities, introducing the possibility of recall bias. This bias is a common occurrence when dealing with events from one’s past, as memory may not always be accurate or complete. However, given the nature of the study and the absence of alternative methods for collecting this data, relying on self-reports from adults about their childhood adversities was unavoidable. Moreover, the sample was self-selected rather than randomly selected, raising concerns about selection bias and generalisability of our results beyond our sample. To address this, researchers can consider random sampling. Additionally, this study does not have a baseline measurement for ASD and proxy PTSD, making it difficult to determine if some non-trauma specific symptoms predated the assessed trauma. Also, trauma exposure was assessed subjectively without severity measures. Lastly, another limitation pertains to the temporal overlap between the Beirut port blast and the COVID-19 pandemic, both of which represented major and concurrent stressors for healthcare workers. Although our instruments explicitly referred to the Beirut port blast as the index trauma when assessing acute and post-traumatic stress reactions, it is possible that participants’ responses were confounded by the broader psychosocial context of the pandemic. In such circumstances, distinguishing between distress specifically attributable to the blast and that stemming from ongoing pandemic-related challenges can be difficult. Examples of those non-specific distress symptoms are loss of interest in previously enjoyable activities, trouble falling asleep, being alert, feeling distant or cut off from people, and trouble experiencing positive feelings. Therefore, some of the reported symptoms may reflect a cumulative or interacting effect of both events or either one rather than a discrete trauma response to the blast alone.

Future directions

For future research directions, longitudinal studies should be conducted across diverse populations, as our study focused solely on healthcare workers. Furthermore, to validate our theory regarding the development of PTSD without prior ASD, future studies should examine populations with minimal risk of continuous exposure to multiple stressors.

In conclusion, childhood adversities, specifically neglect, emerged as strong predictors of both ASD and proxy PTSD. The longitudinal analysis reveals the complex interplay between childhood adversities, ASD and subsequent proxy PTSD. Notably, healthcare workers who survived the Beirut port blast and who did not screen positive for ASD are at a significantly higher risk of developing subthreshold proxy PTSD later if they have a history of neglect during childhood. This underscores the critical importance of comprehensive assessments of childhood adversities in disaster response interventions and looking into subthreshold proxy PTSD diagnosis beyond the full threshold.