Does early peer relationship last long? The enduring influence of early peer relationship on depression in middle and...

Previous studies focus on the health effect of early family relationship rather than early peer relationship. Thus, this study aimed to examine the causal effect of early peer relationship on depression in middle and later life.

Based on the China Health and Retirement Longitudinal Study data 2013-2014 (N = 15,343), this study used the propensity score matching approach to estimate the causal effect of early peer relationship, including establishment (whether having good friends in childhood), engagement (frequency of playing with friends in childhood) and feeling (feeling of loneliness in childhood), on depression in middle and later life, as well as the educational heterogeneity of this health effect.

Elevated feeling of loneliness and reduced engagement of early peer relationship were causally related to elevated depression in middle and later life, but having good friends in childhood was not related to later life depression. For individuals with more education, less feeling of loneliness in childhood had a stronger effect on reduced depression in middle and later life, but more engagement in childhood peer relationship only had a weaker effect on reduced depression in middle and later life.

A retrospective survey and single-item measures of early peer relationship were used, the intermediate link across the life course and potential neurobiological mechanisms were also not empirically examined.

We should focus more on the engagement and quality of early peer relationship, as well as the balance between education and socializing in childhood, to prevent from the detrimental health effect of early peer relationship disadvantage.