No rapid responses to this article have been published yet.  I've just sent
one, after reading the definition of breastfeeding (called 'breast feeding'
in the BMJ) in the article, which I present here for your collective
amusement.
'Breast feeding - women who had had a child since the previous interview
were asked whether they breast fed the child at all, and, if so, how old the
child was when they stoppped breast feeding.  In most cases this information
would have been obtained within a year of the birth.  Even so, reports on
duration of breast feeding were probably less reliable than reports of
whether a child was breast fed or not.'

So, all we know about the breastfeeding in this population is what the
mothers stated, coded into breastfeeding or not breastfeeding, without
respect to exclusivity.

In my response, I said that drawing conclusions about the effect of
breastfeeding based on such a distinction is like drawing conclusions about
the effect of not smoking in a population where some people claimed to have
smoked continuously, while others said they smoked partially, occasionally,
or intensively for short periods.  

I encourage anyone on Lactnet who so desires, to use this comparison when
discussing this article with others.  While we do need studies to clarify to
what degree the effects of breastfeeding on cognitive functioning are
separate from the effects of having a mother who performs well on a test of
cognitive functioning, 'Effect of breast feeding on intelligence in
children: prospective study, sibling pairs analysis, and meta-analysis' by
Der, Batty and Deary in this week's issue of the BMJ is not one of them.

Rachel Myr
Kristiansand, Norway
 

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