Investigating the relative age effect on psychosocial adjustment:Study of children aged 3–15 years

This study examined the association between relative age and psychosocial adjustment in Japanese children aged 3–15 years, as well as the moderating effects of grade level on this association. We conducted a secondary analysis of survey data from 853 Japanese children. Hierarchical multiple regression analysis revealed significant negative associations between relative age and internalizing and externalizing problems; specifically, relatively older children exhibited lower levels of internalizing and externalizing problems. Notably, the moderating effects of grade level, including quadratic and cubic interaction terms, and school enrollment status were not statistically significant in relation to internalizing and externalizing problems. These findings suggest that the effects of relative age on psychosocial adjustment may persist among Japanese children through 15 years of age.