Background Breastfeeding has been associated with higher cognitive scores, better test results and fewer socio-emotional problems in childhood. These outcomes in turn predict social mobility. This study examines the effect of breastfeeding on inter-generational social mobility and the role of two biologically plausible mechanisms: via improved neurological development due to the long-chain polyunsaturated fatty acids in breast milk and via hypothalamic-pituitary-adrenal (HPA) axis functioning due to growth hormones in breast milk.
Methods We use data from two birth cohorts (the 1958 National Child Development Study and the 1970 British Birth Cohort) to examine breastfeeding’s relationship with social mobility. Social class at 10/11 years was based on father’s class. Both class of origin and own social class in adulthood (age 33/34) were measured by the Registrar General’s social class (RGSC). Neurological development was assessed using cognitive tests and assessments of fine motor function. HPA functioning was assessed using socio-emotional behaviour scales and a physical symptoms of stress score.
Results Rates of breastfeeding were higher in the 1958 cohort than the 1970 cohort (43% vs. 21% breastfed 1+ months). Breastfeeding was more socially patterned by 1970, with advantaged mothers being more likely to breastfeed. A propensity score approach matched breastfed and non-breastfed children on a large number of characteristics before estimating the effect of breastfeeding on social mobility. We modelled the odds of upward and downward social mobility conditional on being breastfed for 1 month or more and social class of origin. Results show that breastfeeding increased the odds of upward mobility (1958 cohort: OR 1.25 95% CI 1.13, 1.37; 1970 cohort: OR 1.14 95% CI 1.00, 1.31), and reduced the odds of downward mobility (1958 cohort: OR 0.81 95% CI 0.74, 0.90; 1970 cohort OR 0.79 95% CI 0.69, 0.91). Controlling for the measures of neurological development and stress functioning attenuated the effect of breastfeeding to marginal or non significance. Gender differences in these findings will be discussed.
Conclusion Breastfeeding promotes upward social mobility and protects against downward mobility. The effects appear to operate through enhanced neurological development and more effective stress processes.
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