Background The purpose of this study is to explore whether social relationships of family and school contexts mediate the influence of socioeconomic status (SES) on Chinese adolescents’ mental health. Methods A school-based study was conducted among a sample aged 13–18 in East China (n = 6902). We used scales for measuring social relationships and self-rated mental health. Family SES was computed from subjective socioeconomic status, education and occupation of parents. The mediation model was tested by using Path Analysis in IBM SPSS-Amos. Results The results showed that SES can significantly influence adolescent mental health through parent–child relationship, student–teacher relationship and student–student relationship. The total effect, direct effect and total indirect effect were −0.209 (95% CI = −0.299, −0.136), −0.090 (95% CI = −0.174, −0.007), −0.119 (95% CI = −0.187, −0.078) for boys, and −0.337 (95% CI = −0.478, −0.230), −0.132 (95% CI = −0.283, 0.010), −0.205 (95% CI = −0.351, −0.085) for girls. Conclusion The link between SES and adolescent mental health can be explained by social relationships. Focusing on the parent–child, student–student and student–teacher relationship interventions may contribute to improving the mental health of Chinese adolescents, especially in low socioeconomic groups, as well as female students.

Objectives Our study use the height and weight data of Chinese students aged 7–18 years from 1985 to 2014 to investigate the inequality and changing trend of height and weight of children and adolescents in different regions. Methods Our study extracted data from the 1985, 2000, and 2014 Chinese National Survey on Students' Constitution and Health (CNSSCH) for a comparative analysis of the height and weight of children and adolescents aged 7–18 years in a developed city (Shanghai) and an underdeveloped province (Guizhou). The coefficients of variation (CVs) of height and weight between urban and rural boys and girls were also calculated. Results Since 1985, the height difference between urban and rural areas has decreased from 4.24 to 2.41 cm for boys and 3.72 to 1.99 cm for girls. The weight difference for boys and girls increased from 1.83 to 3.10 kg and from 0.97 to 1.80 kg, respectively. However, from 1985 to 2014, the height and weight differences between Shanghai and Guizhou increased. In addition, from 1985 to 2014, the coefficient of height variation was greater for rural students than urban students while the coefficient of weight variation was greater for urban students than rural students. Conclusions Although the difference between urban and rural areas has recently decreased, the difference between developed area (Shanghai) and underdeveloped area (Guizhou) has increased. In particular, the difference in height and weight between children in developed areas (Shanghai) and non‐developed areas (Guizhou) has become larger since 1985–2014, rather than gradually decreasing over time.