Wednesday, 24 April 2019

"Maternal diabetes, especially GDM, is probably a risk factor for ADHD"

It's coincidental that as I write this post about the findings reported by Lifeng Zhao and colleagues [1] talking about how "Maternal diabetes, especially GDM [gestational diabetes mellitus], is probably a risk factor for ADHD [attention-deficit hyperactivity disorder]" so the BBC news website highlights how screening for gestational diabetes here in Blighty is still a bit of a hit-and-miss affair (see here).

That news report mentions how about a quarter of those mums-to-be who are most at risk of developing pregnancy diabetes - "having a high BMI [body mass index] or being of South Asian or Black Caribbean ethnicity" - did not get screened at all. Left untreated, gestational or pregnancy diabetes can increase the risk of various adverse events including "a baby that grows larger than usual, leading to problems in labour; premature birth; pre-eclampsia and stillbirth."

The Zhao findings - a meta-analysis - continue a theme suggesting that exposure to maternal diabetes, including pregnancy diabetes, seems to increase the risk of various other developmental and behavioural diagnoses also being present in offspring. The primary source material of this blog - autism - has been talked about on various occasions as being one of those developmental/behavioural diagnoses (see here and see here). That ADHD is quite often mentioned in the diagnostic mix when it comes to autism (see here) is another point to make.

The basics of the Zhao paper: a search of the peer-reviewed science literature was undertaken revealing nine studies that fitted the inclusion criteria including "7,218,903 participants." The quality of most studies was ranked as high. The results were interesting in that researchers "did not find significant association between maternal diabetes and ADHD risk (OR: 1.20, 95% CI: 0.96–1.49)." This observation is slightly at odds with the quote titling this post, which Zhao et al put down to the "high heterogeneity" detected among the included studies and their subgroup analysis of case-control studies (n=3).

Also... when it came to looking at another type of study - a cohort study (n=6) - "the meta-analysis demonstrated that maternal diabetes increased the risk of ADHD in offspring by 40%." Further, and bearing in mind the description 'diabetes' covers quite a bit of diagnostic ground, authors zoomed in on one particular 'type of diabetes', that called gestational diabetes (GDM) and looked at any effect. This is where things got a little more interesting as their results, based on four studies, indicated that "GDM exposure increased the risk of ADHD for children by 164%" in Caucasian children. Ergo, although a little mixed, the existing research literature at the time of analysis indicated that maternal diabetes during pregnancy, particularly GDM, *might* have some important effect on risk of offspring ADHD.

I'm not going to say much more at this point in time in terms of potential mechanisms that *might* elevate the risk of ADHD in offspring exposed to pregnancy diabetes. It's likely to be pretty complicated. Given also that GDM appears more often than not alongside other conditions (see here), it's not going to be easy to tease apart what might be the more important issues. Is it inflammation? Is something to do with blood sugar or insulin? At the moment, we just don't know enough...

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[1] Zhao L. et al. The association of maternal diabetes with attention deficit and hyperactivity disorder in offspring: a meta-analysis. Neuropsychiatr Dis Treat. 2019;15:675–684.
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