There was quite a bit of coverage at the end last week about a report published by Essex and Oxford-based researchers that looked at the effects of on-demand feeding versus scheduled feeding. The researchers analysed just over 10,000 thousand babies born in the 1990s and checked whether babies fed in a particular way at 8 weeks and 33 months achieved better academic results later in their lives and whether the well-being of the mothers was affected.
The authors of the study reported an association between being fed on-demand as a baby and higher IQ scores at 8 years and better SATs exam scores at 5, 7, 11 and 14 years. This held true for breastfed and bottle-fed babies. Another effect they uncovered was that mothers who fed on-demand reported lower confidence, higher fretfulness and worse sleep patterns.
Now I’ve mentioned quite a few times the mantra that “correlation does not imply causation”, and so my immediate reaction to seeing this in The Guardian was ‘here we go again’. Journalists often overlook the limitations of correlative studies in favour of neat and tidy story – after all, “this behaviour causes this effect” has a bit more punch than “this behaviour is associated with this outcome, but it may be acting through a third or multiple independent variable(s)”.
For an entertaining and revealing example of this issue, I would recommend reading stand-up mathematician Matt Parker’s ‘mobile phone masts cause increase in birth rates’ hoax story.
My first thought when my wife told me about this story was that, rather than on-demand feeding directly causing the higher IQ scores, it could equally be that a third factor was at play. As a speculative example, it could be that an attentive personality primes a mother to feed on-demand and also, independently, to spend more time with their child on educational development. This is an important distinction because it would mean that mothers wouldn’t be able to improve their child’s academic chances by feeding on-demand, rather they would have to pay more attention to educational development.
The authors were well aware of possible confounders and tried to take into account other differences between the groups to narrow down the possibilities as much as possible. This involved adjusting for family income, the education level of the parents, different parenting styles, the age and sex of children, and general maternal health. After all this, there was still a significant difference – children who were fed on-demand as babies had, on average, IQ scores 4 points better than children who were fed to a schedule.
This study has an advantage over many other correlative studies in that a third group presented itself – mothers who wanted to feed to a schedule but were unable to and so fed on-demand, i.e. they wanted to be in one group (scheduled feeding) but ended up as if they were in the other group (on-demand feeding). Crucially, the children in this third group achieved the same elevated academic achievement as seen in the other on-demand group.
This meant that the authors were able to suggest that the improved academic outcomes weren’t due to having the type of mother who wishes to feed to a schedule, but that they were due to the actual act of being fed on-demand. This relies on an assumption that the mothers in the scheduled feeding group and the attempted scheduled feeding group had similar characteristics, and would therefore have similar approaches in other ways that may affect educational development. This may not be entirely true as other, more subtle differences could exist between these groups, but it’s a tantalising result that merits further investigation. I guess measuring the amount of time spent with the child on learning and development would be something at which to look.
There will still be other factors at play and it is still essentially a correlation, but it starts to narrow down the possibilites. The authors themselves admit the limitations in their study, with the lead author Dr Maria Iacovou telling Science Daily:
“At this stage, we must be very cautious about claiming a causal link between feeding patterns and IQ. We cannot definitively say why these differences occur, although we do have a range of hypotheses. This is the first study to explore this area and more research is needed to understand the processes involved.”
Dr Iacovou was also fairly even-handed on Channel 4 news, rightly highlighting that we still don’t know the mechanism for the observed effects and this is really the first step in establishing a causal relationship.
The final thing to note about the study, is that it was gratifying that the researchers looked at both sides of the issue – the outcomes for the baby (IQ, academic achievement) and the mother (well-being indicators). I’ve written before about the importance of looking at all knock-on effects, as it can be counter-productive to focus solely on the baby if it means a serious detrimental effect on the mother’s mental health.
If on-demand feeding really does drive academic development, then implementing a healthcare strategy to encourage this must take into account the negative impact this may have on the mother and include an appropriate support mechanism. Otherwise, the effectiveness of the intervention will be limited, as mothers will be more likely to give up in favour of a reassuring routine.
As Dr Iacovou said, “mothers are people too”.
Hat-tip to mum-in-law Jenny who sent me this story.
*CC licence: http://creativecommons.org/licenses/by/3.0/deed.en
**CC licence: http://creativecommons.org/licenses/by-nc-nd/2.0/deed.en_GB