I was just going to add this for anyone who is still reading this- its one of the few sibling analysis studies which have been done, apart from the one that tiktok and whatme have been talking about. It makes very interesting reading.
I've just read it now - how interesting. The finding of the study is that
"Most of the observed association between breast feeding and cognitive development is the result of confounding by maternal intelligence. Level of cognitive stimulation at home, mother's educational attainment and age at the birth of the child, child's birth order, and family financial hardship all have independent effects. In fully adjusted analyses, the advantage of breast feeding was small and not significant"
They go on to say that:
"The only previous study that has used the method to assess the benefits of breast feeding examined its relation to 15 indicators of physical health, emotional health, and cognitive ability.10 There were apparent benefits of breastfeeding status and duration for around two thirds of the outcomes. All except cognitive ability were non-significant in the sibling comparisons. They used a 10% level for significance, however, and, judged against the more conventional 5% level, the effect for breastfeeding status was not significant and that for duration of breast feeding marginal. The results from the sibling comparisons in our study and the two studies combined provide no support for a beneficial effect of breast feeding"
And then you go to the conclusion, and it says that
"The broader context of breast feeding should also be considered. Evidence showing the many benefits of breast feeding for the child and mother led the World Health Organization and UNICEF to formulate the Innocenti Declaration,42 which includes exclusive breast feeding for 4-6 months as a global goal. Many of these benefits are equally applicable to developed countries.43,44 Even if it does not enhance intelligence, breast feeding remains ?an unequalled way of providing ideal food for the healthy growth and development of infants.?
So the study says one thing, teh "Conclusion" says teh direct opposite.
Fwiw I have never read this one before, but I'm not surprised - the ones I read were all like this, where the actual data showed no benefits and the "conclusions" said something totally different.
I wonder if Ben Goldacre will ever dare to take this one on :)