Breast feeding and resilience against psychosocial stress

¹ Karolinska Institute, Sweden
² University College London, United Kingdom

^* To whom correspondence should be addressed. E-mail: scott.montgomery{at}medks.ki.se.

Accepted 17 June 2006

	Abstract

Objective:Some early life exposures may result in a well controlled stress response, which can reduce stress-related anxiety. Breast feeding may be a marker of some relevant exposures, so we assessed whether it was associated with modification of the relationship between parental divorce and anxiety.

Design:Observational study using longitudinal birth cohort data. Linear regression was used to assess whether breast feeding modifies the association of parental divorce/separation with anxiety using stratification and interaction testing.

Setting:The 1970 British Cohort Study is following the lives of those born in one week in 1970 and living in Great Britain. This study uses information collected at birth and at ages 5 and ten years for 8958 subjects.

Main outcome measure:Class teachers answered a question on anxiety among 10-year olds using an analogue scale (range 0-50) that was log-transformed to minimise skewness.

Results:Among 5672 non-breast-fed subjects, parental divorce/separation was associated with a statistically significantly raised risk of anxiety, with a regression coefficient (95% confidence interval) of 9.4 (6.1, 12.8). Among the breast-fed group this association was much lower: 2.2 (-2.6, 7.0). Interaction testing confirmed statistically significant effect modification by breast feeding, independent of simultaneous adjustment for multiple potential confounding factors, producing an interaction coefficient of -7.0 (-12.8, -1.2) indicating a 7% reduction in anxiety after adjustment.

Conclusions:Breast feeding is associated with resilience against the psychosocial stress linked with parental divorce/separation. This could be because breast feeding is a marker of exposures related to maternal characteristics and parent-child interaction.

Keywords: HPA axis, breast feeding, longitudinal, resilience, stress

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