Understanding the association between stunting and child development in low- and middle-income countries: Next steps for research and intervention.

Stunting, caused by experiences of chronic nutritional deprivation, affects approximately 25% of children under age five globally (i.e., 156 million children). In this review, evidence of a relationship between stunting and child development in low- and middle-income countries is summarized, and issues for further research are discussed. We focus on studies that measured low height-for-age among children less than 5 years old as the exposure and gross/fine motor skills, psychosocial competencies, cognitive abilities, or schooling and learning milestones as the outcomes. This review highlights three key findings. First, the variability in child development tools and metrics used among studies and the differences in the timing and frequency of the assessments complicate comparisons across study findings. Second, considerable evidence from across many countries supports an association between stunting and poor child development despite methodological differences and heterogeneity in the magnitude of associations. Further, effect sizes differ by developmental domain with greater associations shown for cognitive/schooling outcomes. How stunting influences child development, which domains of child development are more affected, and how the various domains of child development influence one another require further experimental research to test causal pathways. Finally, there is mixed evidence of the additive effect of nutrition + stimulation interventions on child development. However, understanding best methods for improving child developmental outcomes - either through nutrition programs or through integrated nutrition + psychosocial stimulation programs (or nutrition + other program interventions) - is a key area of further inquiry. Given that nearly 40% of children under age five suffer from loss of developmental potential - for which stunting is likely one of the key risk factors - reductions in stunting could have tremendous implications for child development and human capital formation, particularly in low- and middle-income countries.