Short communicationSpillovers between siblings and from offspring to parents are understudied: A review and future directions for research

- A large literature has examined benefits of human capital for an individual's health.
- Relatively little evidence is available on spillovers to family members.
- We conducted a scoping review of the evidence on education-to-health spillovers.
- Horizontal and upward spillovers are understudied compared to downward spillovers.
- (Quasi-)experimental designs and studies from low-resource settings are needed.

BackgroundWhile a large literature has highlighted the protective effects of human capital on an individual's health and to some extent their offspring's health, little evidence is available on the positive spillover benefits of human capital for other family members. We conducted a scoping review of the evidence and identify future directions for research.MethodsWe systematically searched the public health and economics literature on spillover effects from human capital, as indicated by educational attainment, to the health and/or survival of family members. We assessed (i) downward spillover effects (from parents and/or grandparents to offspring), (ii) horizontal spillover effects (from partners, spouses, and/or siblings), and (iii) upward spillover effects (from offspring to their parents and/or grandparents). We assessed the frequency of studies, their study designs, findings, and identified priority areas to inform future research on spillover effects of human capital.FindingsA total of 567 studies met our selection criteria. 286 studies assessed downward spillovers, 22 studies assessed horizontal spillovers, and five studies assessed upward spillovers. Studies on horizontal and upward spillovers found universally positive associations between additional education and better health in family members. The majority of studies used cross-sectional and longitudinal study designs as opposed to (quasi-)experimental designs. Further research is needed on horizontal and upward spillovers and research in low-resource settings, in addition to understanding what level of education matters the most, as well as mechanisms.ConclusionsAlthough positive spillovers of human capital between siblings and from offspring to parents are likely, they have been understudied. Estimates of the returns to human capital that exclude these benefits may be too low.