Abstract:

Post-traumatic stress disorder (PTSD) and depression have high rates of co-morbidity among primary and secondary school students who have experienced a major natural disaster. Some researchers have suggested that overlapping symptoms and dysphoria symptoms of PTSD contribute to co-morbidity, while others have attempted to explain the co-morbidity through a causal relationship between them. However, most of these studies have been based on the hypothesis of common causes, explaining co-morbidity at level of disorders or dimensions, while few studies have investigated patterns of the co-morbidity from the perspective of symptoms.
The Child PTSD Symptoms Scale (CPSS) and Center for Epidemiologic Studies Depression Scale for Children (CES-DC) were administered to two samples of primary and secondary school students one year after the earthquake (Wenchuan earthquake, N = 2530, 47.0% males, M_age = 12.86, SD = 1.96; Ya'an earthquake, N = 723, 47.7% males, M_age = 13.40, SD = 2.29). Gaussian graphical models (GGM) and Bayesian hill climbing algorithms were used to describe patterns of the co-morbidity between PTSD and depression.
It can be seen from Figure 1, overlapping symptoms and emotional numbness were the bridging symptoms. Detachment and future-limited symptoms were bridge symptoms in DSM-IV, were not bridge symptoms in the absence of DSM-IV, and fear, startle response and hypervigilance symptom were bridge symptoms. DSM-IV inaccurately defines the boundaries of PTSD, while intrusion and avoidance symptoms are core symptoms of PTSD. Figure 2 shows depressive symptoms were more likely to trigger PTSD symptoms, while intrusive symptoms triggered avoidance symptoms. The weights of each edge in the Wenchuan and Ya'an networks (all symptoms) are shown in Table 1 and Table 2, respectively.
The above findings were cross-validated in both Wenchuan and Ya'an samples, enhancing the generalizability of the findings and responding to the reproducibility crisis of psychological research. This enlightens clinical practitioners to prioritize the identification of bridging symptoms in the early assessment of clients who have suffered from traumatic events, in order to screen out clients at high-risk of co-morbid with depression. Secondly, the bridge symptoms should also be used as a breakthrough in the intervention process to develop intervention strategies. Finally, during the prognostic process, special attention should be paid to the recurrence of bridging symptoms to prevent the re-emergence of co-morbidity.

Key words: PTSD, depression, network analysis, primary and secondary school students