Tuesday, 15 January 2019

Breastfeeding and ADHD meta-analysed

Readers are asked to consider this post discussing the findings from Ping-Tao Tseng and colleagues [1] concerning breastfeeding and offspring attention-deficit hyperactivity disorder (ADHD) risk, an extension of other blogging chatter on the topic of breastfeeding and other offspring developmental outcomes (see here). The connections? Well, yes, both posts emphasise a possible *association* between breastfeeding and offspring development, but perhaps just as important, both posts will also emphasise how correlation is not necessarily the same as causation and how one has to be careful about making sweeping assumptions when it comes to breastfeeding *choice*...

Same as on the previous paper by Tseng and colleagues [2] I'll mention having a minor part to play in authoring the latest Tseng paper, and how such participation will in no way interfere with my hopefully critical musings on this latest publication.

The name of the research game this time around was to 'meta-analyse' the currently available collected peer-reviewed research literature into some sort of coherent 'where we're at' statement on the topic of breastfeeding practices and offspring ADHD risk. This wasn't about 'making' any new data; just synthesising what is already there on some specific topics: "(1) the difference in the duration of maternal breastfeeding between children with and without ADHD, and (2) the association between maternal breastfeeding and ADHD in children." A total of 11 articles pertinent to those research questions were identified and information was 'boiled down'.

Results: "an association was found between non-breastfeeding and ADHD children (adjusted OR = 3.71, 95% CI = 1.94 to 7.11, p < 0.001)." At first glance this looks like a pretty impressive *relationship* between 'non-breastfeeding' and the presence of a diagnosis of ADHD in offspring. It is, but it might not necessarily mean what you first think. Authors do mention how the early presentation of certain ADHD or possibly related traits might not have been conducive to successful breastfeeding behaviour to the point where a lack of 'cooperation' could have led to less breastfeeding. I'm not saying this is THE reason for the results we reported; merely that it is one possibility to entertain. There may also be other factors to take into consideration too (see here for example) minus any sweeping generalisations.

Whilst I am cautious about making too much of the Tseng findings - subsequent individual studies have reported no link [3] - other, more recent meta-analyses have arrived at similar conclusions to Tseng [4]. Yes, the Zeng paper [4] looked specifically at breastfeeding duration, and yes it was a meta-analysis that overlapped with material used in the Tseng study. But the conclusion - "maternal breastfeeding may reduce the risk of ADHD in children" - is similar, and again suggests closer inspection of any possible relationship specifically focused on the hows-and-whys.

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[1] Tseng PT. et al. Maternal breastfeeding and attention-deficit/hyperactivity disorder in children: a meta-analysis. Eur Child Adolesc Psychiatry. 2018 Jun 15.

[2] Tseng PT. et al. Maternal breastfeeding and autism spectrum disorder in children: A systematic review and meta-analysis. Nutr Neurosci. 2017 Oct 18:1-9.

[3] Schwenke E. et al. Predicting attention deficit hyperactivity disorder using pregnancy and birth characteristics. Arch Gynecol Obstet. 2018 Nov;298(5):889-895.

[4] Zeng Y. et al. Association between the different duration of breastfeeding and attention deficit/hyperactivity disorder in children: a systematic review and meta-analysis. Nutr Neurosci. 2018 Dec 21:1-13.

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