I’m not the first person to comment on this study and I probably won’t be the last, either. Others have commented upon its most obvious flaw: the small sample size (6 women in each group) makes it impossible to determine whether the results are significant or the result of random chance. But having read the full-text article (sent me by a reader – thank you 🙂 ), I find myself asking even more questions about the validity of the study design and their hypothesis:
*The results that were looked at were not the absolute levels of brain response to the crying of either the mothers’ own baby or that of another baby, merely the difference between them. Why are the absolute levels (i.e, how acutely a mother’s brain responds to crying of an infant) not important as well? Why was there no attempt to assess these levels of brain activity using a generic baby cry before these women gave birth – perhaps there were significant differences in their brain responses that have nothing to do with mode of birth (intended or actual)?
*The normal response of a mother when she hears her baby crying is that of distress and an urge to stop the crying with her actions. So why are areas of the brain associated with reward expectation and positive emotions lighting up in these women, with more baby-specific activity seen in the vaginal delivery women? In fact, the whole idea of mapping specific areas of the brain with fMRI and correlating them with complex human emotions seems to still be in its infancy. I’m not sure one could, at this stage, come to the conclusions the researchers did regarding emotional processes based upon the current knowledge, but it’s really not my field of expertise.
*The mothers were all given tests which assessed the presence of intrusive thoughts (Yale Inventory of Parental Thoughts and Actions/YIPTA) and postpartum depression (Beck Depression Inventory). Interestingly, the vaginal delivery moms’ depression index score trended higher than that of the CS moms…and this was nearly significant (p value=0.059). What’s more, there was a rather strong positive correlation between the woman’s Beck score and the response of the frontal lobe of her brain to her own baby’s cry. If it’s legitimate at all to deduce anything from this small sample of women, could it not be also that women who have a vaginal birth may exhibit more depressive symptoms and these affect their brain response to their baby’s cry (perhaps with greater distress)? Later on in the discussion, the researchers state that since cesarean section is associated with greater incidence of postpartum depression (far from established, and in any case, the article they reference doesn’t seem to differentiate between planned and unplanned CS’s) and maternal depression has a negative psychological effect on the baby (true, and I’ve discussed this before in the context of CIO), if their study is replicated, how does it support their statement that “CSD mothers are less sensitive to their infant and this may contribute to the possible link between CSD and a range of adverse psychosocial effects, including postpartum depression (PPD)”?
*Most important is the reality check: the women were asked to rate their own emotional response to the crying, the result being that
There were no signiﬁcant differences in emotional ratings of baby-cry or control-sound stimuli between VD and CSD subjects. In addition, across all subjects, there were no signiﬁcant differences between emotional response scores (0–3) between own baby-cry (2.7 ± .3) and other baby-cry (2.6 ± .5).
So even assuming the results of this study are valid, if there is no real effect on perceived emotion or maternal behavior (the latter was not assessed, and probably should have been, though even then I would guess that bonding is more of an emotional process than a behavioral one) – who cares whether or not certain brain areas light up more or less? Maybe next time they should also throw some adoptive mothers of babies into the mix (or what the heck, some fathers) for comparison?
All in all, while the study is intriguing, the interpretation of the results, and the study design and assumptions, need more than a bit of work.
UPDATE Sep. 13th: Colin, the Skeptic Dad, has an interview with the study’s lead author, Dr. James Swain. Good work, Colin!