This afternoon, as I worked on a study on children of depressed mothers, I came across an article about the effects of breastfeeding on the brain electrical activity of babies. I usually only review recent research, but this study is worth an exception, especially in light of our recent review of Hanna Rosin’s article on the Atlantic magazine questioning the strength of the link between breastfeeding and IQ (see my review here).
In 2004, Dr. Nancy Jones and a team at Florida Atlantic University published a study on the brain electrical activity of infants of depressed mothers. They recruited 31 depressed and 47 non-depressed mothers and their infants. 27% of the depressed mothers were breastfeeding. This compared to 52% of the non-depressed mothers. The authors were interested in examining the association between breastfeeding and the EEG patterns of these infants, and in particular pre-frontal asymmetry.
There is a large body of research showing that relative right prefrontal asymmetry (greater right than left activation) is associated with withdrawal-related behaviors, including emotional responses to some (but not all) negative emotional stimuli (fear and sadness for example). In contrast, relative left prefrontal asymmetry is associated with approach-related behaviors and positive affect. With few exceptions, depressed people display decreased activity in the left prefrontal regions relative to the right. It is believed that this reflects both anomalies in the processing and experience of positive and negative emotions, as well as anomalies in the systems that control approach motivation (“I want to get of the house and enjoy the outside”) leading to anhedonia (lack of pleasure on pleasurable activities). Surprisingly however, many investigators have shown that infants of depressed mothers also display relative right prefrontal asymmetry, which suggests that this pattern is present before people become depressed.
Back to Jones’ study. The authors of the study measured EEG activation in these infants during a quiet activity (being held by their mothers or sitting on a high chair). The authors found that babies of depressed mothers who were bottle fed displayed significantly less left frontal activation than babies of depressed mothers who were breastfed. Surprisingly, babies of depressed mothers who were breastfed did not differ from the babies of non-depressed mothers in their brain activation.
It would be easy to just conclude that breastfeeding served as some sort of protective factor in these at-risk babies, making them ‘look’ more like their non-at-risk peers. However, the story is not that simple. The babies temperament also affected breastfeeding, in that more reactive babies seemed to elicit less breastfeeding than ‘easy’ babies. Temperament has also been associated with EEG patterns, with reactive babies showing more right frontal asymmetry. So it is possible that what we have here is a two way street. In one direction, easy babies (who have left-frontal asymmetry) elicit more breastfeeding, while more difficult babies (who have right frontal asymmetry) elicit less breastfeeding. However, this can not be the only way, since among the non-at-risk babies, breastfeeding did not appear to be related to EEG pattern. So although maternal breastfeeding behaviors are clearly affected by the babies temperament, it seems that breastfeeding also affects the babies temperament and EEG patterns.
The authors provide a nice conclusion:
Specifically, infants of depressed mothers who breastfed did not demonstrate the greater relative right frontal EEG asymmetry (nor the left frontal hypoactivity) compared to the bottle fed group. Moreover, increased positive affect was apparent in 3-month-old infants of breastfed compared to the bottle-feeding/depressed group suggesting that breastfeeding should be examined further as a potential intervention factor for depressed mother and their infants.
Jones, N. (2004). Patterns of brain electrical activity in infants of depressed mothers who breastfeed and bottle feed: the mediating role of infant temperament Biological Psychology, 67 (1-2), 103-124 DOI: 10.1016/j.biopsycho.2004.03.010
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