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The literature has shown that mobile phone addiction is an important risk factor for depression. However, the internal mechanisms of mobile phone addiction leading to depression are still not clear. This study examined the mediating role of sleep quality and moderating role of peer relationships in the association between mobile phone addiction and depression. A sample of 450 Chinese medical students were recruited to complete measures of mobile phone addiction, depression, sleep quality and peer relationships. In this study, SPSS 25.0 and macro PROCESS were used to conduct statistical analysis on the collected data. The results showed that sleep quality partially mediated the association between mobile phone addiction and depression. Moreover, the effect of sleep quality on depression was moderated by peer relationships. The present study can advance our understanding of how and when mobile phone addiction leads to depression. Limitations and implications of this study are discussed.

Background: Parents who have lost their only child are known as Shidu parents in China. Losing an only child is an enormous tragedy for parents that can trigger severe depressive symptoms. Few studies have explored the influence of cultural beliefs and social support on depressive symptoms. Objective: This study aimed to explore the relationship between culture-related grief beliefs, social support and depressive symptoms among Shidu parents in rural China. Method: This cross-sectional study was conducted in Sujiatun district of Shenyang, China. Data were collected from November 2019 to February 2020 from 228 rural Shidu parents. Questionnaires consisted of the Center for Epidemiologic Studies Depression Scales (CES-D), the Culture-related Grief Beliefs of Shidu Parents Questionnaire (CBSQ), the Social Support Rating Scale (SSRS), and demographic and bereavement-related information. Hierarchical multiple linear regression analysis was conducted to examine the associations among culture-related grief beliefs, social support and depressive symptoms. Results: Of the 228 Shidu parents, 87.0% reported depressive symptoms (CES-D ≥ 16). The mean age of the participants was 62.91 years, ranging from 50 to 86. Regression analysis indicated that parents' younger age, lower education level and debts were prominent risk factors for depressive symptoms. Perceived stigma (a subscale of CBSQ) was positively associated with depressive symptoms. Social support was negatively associated with depressive symptoms. Conclusions: Given the high prevalence of depressive symptoms in rural Shidu parents, there is a critical need to reduce perceived stigma and increase social support to alleviate depressive symptoms among Shidu parents in rural China. 'Shidu parents' in China refers to parents who have lost their only child. The prevalence of depressive symptoms among Shidu parents is 87.0%. Reducing perceived stigma and increasing social support are essential to alleviate Shidu parents' depressive symptoms.

Let H=(V,E) be a hypergraph with vertex set V and edge set E. S⊆V is a feedback vertex set (FVS) of H if H has no cycle and τc(H) denote the minimum cardinality of a FVS of H. Chen et al. [IWOCA,2016] has proven if H is a linear 3-uniform hypergraph with m edges, then τc(H)≤m/3 . In this paper, we furthermore characterize all the extremal hypergraphs with τc(H)=m/3 holds. This result has a direct application to Tuza’s conjecture.