Child Development Risk Factors For Adverse Outcomes In Developing Countries

Series

Child development in developing countries 2 Child development: risk factors for adverse outcomes in developing countries
*Susan P Walker,*Theodore D Wachs, Julie Meeks Gardner, Betsy Lozoff, Gail A Wasserman, Ernesto Pollitt, Julie A Carter, and the International Child Development Steering Group†

Poverty and associated health, nutrition, and social factors prevent at least 200million children in developing countries from attaining their developmental potential. We review the evidence linking compromised development with modifiable biological and psychosocial risks encountered by children from birth to 5 years of age. We identify four key risk factors where the need for intervention is urgent: stunting, inadequate cognitive stimulation, iodine deficiency, and iron deficiencyanaemia. The evidence is also sufficient to warrant interventions for malaria, intrauterine growth restriction, maternal depression, exposure to violence, and exposure to heavy metals. We discuss the research needed to clarify the effect of other potential risk factors on child development. The prevalence of the risk factors and their effect on development and human potential are substantial.Furthermore, risks often occur together or cumulatively, with concomitant increased adverse effects on the development of the world’s poorest children.

Lancet 2007; 369: 145–57 *Lead authors †Steering group listed at the end of the paper This is the second in a Series of three articles about child development in developing countries Epidemiology Research Unit, The University of the West Indies, Mona,Jamaica (Prof S P Walker PhD); Department of Psychological Sciences, Purdue University, West Lafayette, IN, USA (Prof T D Wachs PhD); Caribbean Child Development Centre, University of the West Indies, Mona, Jamaica (J Meeks Gardner PhD); Center for Human Growth and Development and Department of Pediatrics and Communicable Diseases, University of Michigan, Ann Arbor, MI, USA (Prof B Lozoff MD); Divisionof Child and Adolescent Psychiatry, Columbia University, New York, USA (Prof G A Wasserman PhD); University of California, Davis, CA, USA (Prof E Pollitt PhD); Centre for International Health and Development, Institute of Child Health, University College, London, UK (J A Carter PhD) Correspondence to: Prof Susan Walker, Epidemiology Research Unit, Tropical Medicine Research Institute, Universityof the West Indies, Mona, Kingston , Jamaica susan.walker@uwimona. edu.jm

Introduction
The first paper in this series showed that more than 200 million children under 5 years of age in developing countries are not fulfilling their developmental potential.1 In this paper, we review biological and psychosocial risk factors that contribute to these adverse outcomes. We use the term risk factor torefer to biological and psychosocial hazards that can compromise development. Figure 1 shows pathways from poverty to poor child development. Development consists of linked domains of sensori-motor, cognitive-language, and socialemotional function.2 Poverty and the socio-cultural context increase young children’s exposure to biological and psychosocial risks that affect development through changes inbrain structure and function, and behavioural changes. Although we consider risks individually in this paper, children are frequently exposed to multiple and cumulative risks.3 As risks accumulate, development is increasingly compromised. Data from Guatemala4 (figure 2) show a linear decrease in adolescents’ school achievement and cognition with an increase in risk factors encountered by age 3years. As discussed in the first paper in this series,1 children’s ability on school entry is an important component in determining their progress in school. We therefore focus on risk factors in early childhood that affect readiness for school and subsequent school performance. School readiness is affected by cognitive ability, social-emotional competence (affects classroom behaviour and peer...