nkvd, thanks - I know that study and found it once more by repairing your link.
I asked for a study and you sent me one - however, it doesn't show what you are saying it shows - you are saying that this is a study which shows no connection between breastfeeding and long-term benefit (in this case, intelligence).
It doesn't - and I am not being picky, here, but scientific, or trying to be....the stats involved are at the edge of my ability to critique, so I may not be getting it right.
It shows that exposure to LCPUFAs is not a factor in (their chosen method of measuring) IQ at age 4.
The authors' own abstract is indeed confusing, but in fact what they have shown is buried in the discussion:
"Our finding that total intake of DHA in milk up to age 6 months was not linked with subsequent intelligence provides a further indication that the association between breast milk and cognitive development may not be due to the LCPUFA content of the milk."
I am not sure how significant it is, but the babies in the 'breastfed' group were breastfed for a mean of 20.5 weeks - obviously many would be bf for less than this time, and none for more than 6 mths (because they did not collect data after this date). It may be that another study not looking specifically at LCPUFAs exposure and with a greater variance of social class and maternal IQ could have found something different (higher education and IQ were seriously over-represented in the bf group, and only 6 per cent of them were on means-tested benefits, which reduces the effect of removing confounding factors).