Traumatic events have been recognized as important precipitants of sleep problems. Meanwhile, traumatic insomnia is one of the criteria for diagnosing post- traumatic stress disorder (PTSD). However, whether trauma-induced sleep problems are secondary symptoms of PTSD or a core feature of PTSD has not yet reached a consistent conclusion. Recently, the emerging cross-lagged panel network analysis method has played an important role in understanding the role of symptoms in psychopathology. The advantage is that the role of each symptom can be systematically analyzed, and the longitudinal predictive pathway of each symptom can be estimated, thereby inferring the leading symptoms of psychiatric disorders. The present study aims to explore the role of trauma-induced sleep problems in the evolution of PTSD among children and adolescents through the cross-lagged panel network analysis. Three months after the Zhouqu debris flow, we started this 2-year longitudinal study. Three assessments were performed at 3 months (T1), 15 months (T2) and 27 months (T3) after the disaster. We enrolled students from 2 primary schools and 3 secondary schools in the hardest-hit areas. Ultimately, 1, 460 children and adolescents completed three rounds of evaluation. At T1, there were 702 students from grades 4 to 6, and 758 students from grades 7 to 9. The average age of the participant was 12.89 (SD = 2.29). Symptoms of PTSD were assessed with the University of California at Los Angeles PTSD Reaction Index based on the DSM-IV. The cross-lagged panel network analysis was conducted using R packages glmnet and qgraph. Results showed that at T1.T2, sleep problems had the highest out-expected influence centrality, followed by physiological cue reactivity. They were sources of activation for the nodes receiving its edges, that is, they were easy to activate other symptoms in the PTSD network. Sleep problems at T1 positively predicted a lot of other PTSD symptoms at T2, including intrusive thoughts, nightmares, flashbacks, emotional cue reactivity, restricted positive affect, restricted negative affect, irritability/ anger, hypervigilance and exaggerated startle response. The results also revealed several indirect influence paths such as sleep problems predicting nightmares then affecting flashbacks. However, when it comes to T2. T3, it is detachment rather than sleep problems that had the highest out- expected influence. It positively predicted diminished interest, restricted positive affect, sleep problems and irritability/anger. We also found some feedback loop: detachment. restricted positive affect.diminished interest. detachment. This is the first study to explore activation paths of PTSD symptoms among children and adolescents through the cross-lagged panel network analysis. These findings have improved the understanding of the role of trauma-induced sleep problems in the long-term development of PTSD. The results showed that sleep problems at 3 months after the disaster activated a large number of symptoms in PTSD at 15 months after the disaster. Therefore, it is inferred that early sleep problems were the core symptom in the development of PTSD among children and adolescents in the early post-disaster period. However, its predictability decreased in the later period (15 months to 27 months). In conclusion, these findings emphasize the time specificity of the impact of traumatic sleep problems on PTSD symptoms. We recommend that trauma-induced sleep problems should be given greater priority in the diagnostic criteria for PTSD among children and adolescents in the early post-disaster period. Meanwhile, early psychological assistance should vigorously develop treatments based on sleep problems to prevent the occurrence and development of PTSD. One year or longer after the traumatic event, the intervention target should be set to physiological cue reactivity and detachment.
