(This piece first appeared on the Gifted Ireland blog.)
Last week, the media was all aflutter with news that breastfeeding makes children smarter which, in turn, leads to a higher level of education and, by extension, better paid employment. Breastfeed your kids if you want them to be smarter and earn more (and, perhaps, choose an altogether more pleasant nursing home for you!) was the message mainstream media sent us. Newspapers here, in the US and in the UK told us that breastfed children have higher IQs and earn more money.
Before I go any further, let me declare my own personal bias. I am a breastfeeding advocate and have been for as long as I can remember. I breastfed my own children until they self-weaned (which was five-and-a-half years in one case), donated my spare milk to the milk bank and am a firm believer in the healing powers of mothers’ milk for pretty much every ailment and difficulty associated with early childhood. Nothing, therefore, would make me happier than to read new research making stronger and further arguments for breastfeeding.
Unfortunately, the study cited in this longitudinal study from Brazil doesn’t do that. The fact that breastfed children have higher IQs (or artificially-fed children have lower IQs, depending on how you look at things) is not news. Instead, what is new is that the authors of this study claim that breastfeeding causes higher IQs, which in turn causes higher educational attainment, which in turn causes higher incomes.
Many women I’ve heard from in the past few days have been saying – tongue in cheek for the most part – that their babies will be geniuses on account of the fact that they have been breastfed. Some, who are part of the GAS network of support groups, have wondered if their children are Gifted because they were breastfed and if they might be more Gifted if they had been breastfed for longer.
Sadly, the findings of this study don’t support that theory. For a start, we already know that there is an inherited element to intelligence that infant feeding has no bearing on. We are also aware that children who are of gifted intelligence don’t necessarily do well at school for a variety of reasons (we won’t go into those reasons here – that’s a whole other blog post!). In addition, even those who do well at school and go on to attain BAs, MAs and PhDs don’t always earn more than those who are not as well educated: The sense of global justice that often accompanies gifted intelligence sees those with the highest IQs busy themselves in academia, research and other areas that don’t necessarily bring the most financial reward. Or, we find that they reap the greatest rewards pursuing their passions – which doesn’t necessarily bring riches, either.
Crucially, with regard to giftedness, this article finds that the difference in IQ between the most extreme groups was nearly four points, or less than a quarter of a standard deviation. While this is certainly statistically significant, giftedness is marked by the presence of two standard deviations above the mean. More importantly, the margin of error in IQ tests is five points, so the difference of not quite four points between the most extreme groups make the findings of this study meaningless.
The difference in education was just 0.9 years, which is roughly a quarter of a standard deviation. Again, this isn’t a difference big enough to have push someone’s education up a level; it’s just over a month, really. The difference in income was reported at about a third of the average income in Brazil. It’s a bit of a leap to extrapolate that figure into non-Brazilian populations (as much of the mainstream media did) because there are so many variables associated with income.
Of interest is that, of the 3,493 adults in the study, those who were unemployed were excluded from the analysis. Michele Pippet, Gifted Ireland’s Treasurer, is a psychologist, and in her work with gifted adults, Michele has noticed that, while there are many who are hugely successful, there are many who are un- or under-employed. So excluding unemployed adults who were breastfed from the study skews the results somewhat.
The other difficulty with these findings is that the study didn’t measure home environment characteristics during childhood; nor did it factor in maternal-infant bonding. It, therefore, does not explore the possibility that associations identified might be attributable to the biological components of breastmilk itself, mother-infant bonding or the intellectual stimulation of breastfed children. I have to wonder, though, how exactly they did that – because the article in the Lancet doesn’t give any indication. My research in the area of breastfeeding leads me to believe that, when a child is breastfed from the breast (as opposed to fed expressed breastmilk from a bottle), the separation of the benefit of the actual milk from other influencing factors is nigh on impossible.
I’m also concerned with how this study defined ‘breastfeeding’. Once the babies who had been signed up to study were 19 or 42 months old, researchers asked their mothers how they had been fed. While exclusive breastfeeding was noted, it was excluded from the analysis of the study which I find a staggering omission. Exclusive breastfeeding to six months of age is the minimum recommended by the WHO (though I can’t be sure when that was first recommended, I know it was more than 20 years ago) and it should surely be seen as relevant in a study like this. I also wonder at the value of asking mothers so long after their children were born. Whatever about the children who were 19 months old, those who were 42 months old may well have had younger siblings by then and we all know how easy it is to get details of your children’s babyhoods confused.
This study also has a large percentage of ‘loss’. That is, there is a large number of candidates who were lost from the final number of participants (including 325 who are known to have died before the study concluded). The study started with 5,914 and finished with 2,421 participants. This represents a loss of 41% which, to social researchers, is a suboptimal rate. In general, a loss rate of 20% is considered good, while a 40% loss rate is not considered acceptable. Further, we’re not told if this loss includes the unemployed who were excluded from the findings, or if this loss of 41% is further compounded by more exclusions. So we really do have to treat these results with caution.
The bottom line with these results was that men in the survey had slightly higher IQ results than women (again, there are difficulties with the Wechsler Adult Intelligence Scale, third version – the test used), women attained higher educational results than men, and men earned more than women. Which is pretty much how things play out in every country in the world regardless of how and what babies were fed.
I would treat the results of this study with caution: Breastfeed your children if you want to do what’s best for them, but don’t expect it to turn them into genii as a result.
If you would like to read the study in its entirety, it can be downloaded here.