Longitudinal associations between pandemic post-traumatic stress symptoms and subsequent non-suicidal self-injury in adolescents: A multiple mediation model.

BACKGROUNDS: PTSD is one of the most common conditions after people have experienced trauma. While previous studies have found a link between PTSD and non-suicidal self-injury, (NSSI), few studies have longitudinally explored this relationship and the underlying mechanisms. AIMS: This study explored adolescent NSSI frequency after COVID-19 lockdown experiences, the relationship with early PTSD symptoms, and the mediating role of depression and sleep problems. METHODS: A cohort of 1609 adolescents completed two surveys during and after the national lockdown in China; one month into the lockdown and six months later; which assessed demographic and pandemic-related exposure variables; PTSD, depression, sleep, and NSSI. Mediation analyses and hierarchical regression were employed to examine the relationships and the paths between these variables. RESULTS: The NSSI rate was found to be 31.9 % after the three-month lockdown, with 20.6 % of adolescent participants reporting sleeping disorders, and 33.9 % indicating probable depression. Adolescents who had earlier PTSD symptoms, often smoked and/or drank, and had current depression and sleep disorders reported greater NSSI. Early PTSD symptoms were found to predict later NSSI and were mediated by sleep problems and depressive symptoms. Specifically, PTSD avoidance and numbing symptoms were significantly associated with NSSI above and beyond the depressive symptoms, sleeping problems, and the other covariables. CONCLUSION: It is necessary to be vigilant about the increased risk of NSSI in adolescents who have experienced extended pandemic lockdowns. Preventing early adolescent PTSD symptoms, especially avoidance and numbness, and helping teenagers quit smoking and drinking could reduce the risk of sleep disorders, depression, and NSSI.

Embankment seismic fragility assessment: A case study on Xi'an-Baoji expressway (China).

Although embankment seismic damages are very complex, there has been little seismic fragility research yet. Researches on seismic fragility of bridges, dams and reinforced concrete (RC) structures have achieved fruitful results, which can provide references for embankment seismic fragility assessment. Meanwhile, the influencing degrees of retaining structures, such as retaining walls on the embankment seismic performances are still unclear. The K1025+470 embankment of the Xi'an-Baoji expressway was selected as the research object, and the finite difference models of the embankment fill-soil foundation system and embankment fill-soil foundation-retaining wall system were established. The ground-motion records for Incremental Dynamic Analysis (IDA) were selected and the dynamic response analysis were conducted. Probabilistic Seismic Demand Analysis (PSDA) was used to deal with the IDA results and the seismic fragility curves were generated. Based on the assessment results, the influences of the retaining wall on the embankment seismic fragility were further verified. The research results show that regardless of which seismic damage parameter is considered or the presence or absence of the retaining wall, larger PGAs always correspond to higher probabilities of each seismic damage grade. Seismic damages to the embankment fill-soil foundation-retaining wall system are always lower than those of the embankment fill-soil foundation system under the same PGA actions, thus, the retaining wall can decrease the embankment seismic fragility significantly.