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One of the other themes that was touched upon in that post was the question of whether issues with vitamin D noted in cases of autism may actually tie more strongly into some of the comorbidity which can also present alongside the core triad/dyad of symptoms. I used the example of depression in that case, extrapolating from the observations made by Anglin and colleagues  in their systematic review and meta-analysis of the combined peer-reviewed data up to 2011, knowing that the presence of autism and depression have some overlap in the research literature. I'll be talking more about this depression-vitamin D link/suggestion in a forthcoming post.
I want to continue that theme in today's post discussing the study by Bener and Kamal  (open-access here) who concluded: "Vitamin D deficiency was considerably higher in ADHD [attention deficit hyperactivity disorder] children compared to healthy children". Before anyone takes offence at the authors' use of the words 'healthy children' to denote their control group, I would have been minded to suggest the words 'asymptomatic controls' if I were writing this paper. I should perhaps also direct you to another paper by some of the same authors which also presents data on what appears to be the same cohort .
Their results, based on a case-control study including various direct and indirect measures covering physicians notes and biochemical data for children/young adults living in Qatar, included a number of potentially important snippets of information not least: "Multivariate logistic regression analysis revealed that household income, poor relationship between parents, mothers' occupation, consanguinity, BMI in percentiles, low duration of time under sun light, physical activity, low serum calcium level and low vitamin D level were considered as the main risk factors associated with the ADHD after adjusting for age, gender and other variables" (sorry for the long quote).
Looking at some of these factors linked to ADHD risk, I was immediately taken by their BMI (body mass index) data and in particular: "Overweight (7.7% vs 9.4%) and obesity (4.6% vs 7.7%) were significantly lower in ADHD children compared to their counterparts". This kinda flew in the face of other data which have started to emerge suggesting that ADHD may actually increase the risk of weight issues, as per the findings from Fliers and colleagues  for example. Of course I accept that we are looking at different populations, different genetics with very different eating habits and different environments so one has to be slightly cautious before making too much of a leap. But it is an interesting disparity and may be something important in future.
Back to the vitamin D issue identified in the Bener/Kamal paper, it was also interesting to note that quite a few of the other nutritional measures employed during the study also came up with lower results when compared to controls. So, group average levels of calcium, phosphorus, magnesium and potassium in serum were all lower compared to controls. This did make me wonder whether there is a more general micronutrient deficiency present in the ADHD cases over and above just something specific to vitamin D. I'll for example, take you back to a fairly recent post I did on the Julia Rucklidge paper talking about 'a vitamin-mineral mix for ADHD' (see here) as perhaps being pertinent here too.
A quick search around the accompanying research landscape suggests that vitamin D is still something of an unexplored area when it comes to cases of ADHD. That one of the only other studies done on vitamin D and ADHD is another study by Rucklidge and colleagues  is coincidental, although also potentially important given their observation within their cohort that: "Among the nutrients recorded at baseline, substantial deficiencies (27%) were only observed for vitamin D".
If one is to accept that ADHD or ADHD-like behaviours can and do feature across some cases of autism (see here) it is possible to see how problematic it might be to disentangle which condition or which behavioural characteristics of each condition, may show the strongest connection to something like a vitamin D deficiency. I'm not ruling out autism or autistic behaviours as being the primary driver of risk for vitamin D issues but to say anything further at this point time in terms of a causal relationship (whichever way) is perhaps a little premature despite some research eagerness. And given what seems to emerging when it comes to other dietary-based interventions 'for autism' with a side of ADHD, I'd be minded to say the focus on exactly what are the primary effects of such strategies in diagnostic terms should be near the top of any research agenda. RDoC anyone?
To close, taken from one of my favourite operas, Toreador! [song]
 Anglin RE. et al. Vitamin D deficiency and depression in adults: systematic review and meta-analysis. Br J Psychiatry. 2013 Feb;202:100-7.
 Bener A. & Kamal M. Predict attention deficit hyperactivity disorder? Evidence -based medicine. Glob J Health Sci. 2013 Nov 27;6(2):47-57.
 Kamal M. et al. Is high prevalence of vitamin D deficiency a correlate for attention deficit hyperactivity disorder? ADHD Attention Deficit and Hyperactivity Disorders. 2014. DOI: 10.1007/s12402-014-0130-5
 Fliers EA. et al. ADHD is a risk factor for overweight and obesity in children. J Dev Behav Pediatr. 2013 Oct;34(8):566-74.
 Rucklidge JJ. et al. Moderators of treatment response in adults with ADHD treated with a vitamin-mineral supplement. Prog Neuropsychopharmacol Biol Psychiatry. 2014 Apr 3;50:163-71.
Bener A, & Kamal M (2013). Predict attention deficit hyperactivity disorder? Evidence -based medicine. Global journal of health science, 6 (2), 47-57 PMID: 24576365