Objective This study aimed to examine whether there is any remaining association between grandparental poverty and grandchildren's body mass index (BMI) and depression, after controlling for parental poverty and other parental characteristics.Methods Data used in this study were gathered through the Child Living Standard Survey (Kodomo no Seikatsu Jittai Chosa) conducted by the Tokyo Metropolitan government in 2016. The survey questionnaires were mailed to all children in grades five, eight, and eleven who lived in four districts of Tokyo. Data for grades five and eight were used for analysis. First, the children were divided into four groups according to their grandparents' and mothers' poverty status, and their BMI and depression were compared. Then, structural equation modeling was used to fit a model where grandparental poverty was associated with parental poverty and parental BMI and depression, and they, in turn are associated with grandchildren's BMI and depression, as well as directly associated with them. BMI and Birleson Child Depression Scale (DSRS-C) were used for grandchildren, and BMI and K6 depression scale were used for parents.Results Children whose grandparents were poor but parents were not poor had a higher depression index than those who were not poor at all. However, the result did not hold for BMI. The goodness of fit of the SEM model was CFI=0.907, RMSEA=0.036 for BMI; CFI=0.810, RMSEA=0.037 for depression. The findings indicated that grandparental poverty was associated with grandchildren's BMI only through parental BMI, whereas for depression, grandparental poverty was associated with parental poverty and parental depression, which in turn were associated with grandchildren's depression. Furthermore, an association was found between grandparental poverty and grandchildren's depression even after controlling for parental poverty and parental depression.Conclusion Grandparental poverty is associated with grandchildren's depression through means other than parental poverty and parental depression. To combat this, it is necessary to not only adopt the "3-generation approach" which focuses on child and parent's current conditions, but also to implement policy to assist children when they become parents in the future. As for BMI, effective policies should be put into place to combat parents' and children's current weight problems.
Keywords: 3-generation approach; SEM analysis; child poverty; inter-generational transmission of poverty.