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Whilst receiving some media exposure at the time of publication, the Chaidez paper was slightly over-shadowed by another potentially interesting autism development published at a similar time by Warren and Klin (briefly discussed in a previous post) looking at eye gaze in young infants.
I suppose it's to be expected that chatter about [potential] novel early markers for autism will garner more headlines that the mundane task of scientific replication. Indeed, replication is once again the name of the game when it comes to the Chaidez paper, building on quite a bit of previous research suggesting that functional gastrointestinal (GI) issues can and do appear alongside quite a few cases of autism.
The details of the Chaidez paper are pretty straight-forward insofar as asking parents of children involved in the CHARGE study (beincharge!) to report on their children's behaviour and bowel activity via a couple of questionnaires (the Aberrant Behavior Checklist and the CHARGE Gastrointestinal History Questionnaire (GIH)). According to the study press release, the CHARGE GIH questionnaire "measures such disorders as abdominal pain, diarrhea, constipation and difficulty swallowing" but as yet I've not been able to find out too much about it's content validity and reliability within the peer-reviewed domain. Since I've mentioned CHARGE, I'll also draw your attention to some interesting research on air pollution and autism which I'll be posting about fairly soon.
Anyhow, based on responses from just shy of 1000 participants spread across categories of autism spectrum disorder (ASD) diagnosed, developmental delay (DD) diagnosed and typically-developing (TD), the results corroborate quite a lot of previous research undertaken in this area: "Compared to TD children, those with ASD [aOR 7.92 (4.89-12.85)] and DD [aOR 4.55 (2.51-8.24)] were more likely to have at least one frequent GI symptom". Functional bowel issues do seem to be more commonly reported in cases of ASD (and DD) compared with asymptomatic controls. A shocker, I know. Oh and just in case I have to say it again, parental reports of offspring GI complaints in relation to autism are actually quite sensitive as per the findings by Gorrindo and colleagues**.
There are some other very interesting details also discussed in the Chaidez paper and commentary which are worthy of comment. A long quote for you: "The researchers said that the study suggests that a chronic GI symptom, which can cause pain, discomfort and anxiety, could contribute to increased irritability and social withdrawal, particularly in children with deficits in social and communication skills. For children with autism, hyperactivity and repetitive behaviors may represent coping mechanisms for physical discomfort".
It's not rocket science to understand that having a functional bowel issue, or perhaps even something more pathological, which may impinge on a persons quality of life and may even cause some significant amount of physical and psychological distress, is probably going to [variably] show on a person's day-to-day behaviour. I think back to the paper by Kushak and colleagues*** (which was discussed in this post) on lactose intolerance in cases of autism and their quote: "Lactase deficiency not associated with intestinal inflammation or injury is common in autistic children and may contribute to abdominal discomfort, pain and observed aberrant behavior". I've used food as the example to highlight this issue but am not as yet, making any connection with those issues identified by Chaidez et al. Indeed, in a similar vein, I'm also brought back to the findings of Micah Mazurek and colleagues which talked about gut issues being potentially linked to anxiety and sensory issues in relation to autism as further evidence for that gut-brain or rather gut-behaviour relationship. The important mention that autism is rarely, in ESSENCE, a stand-alone condition is also worthwhile reiterating here.
You can probably tell that I'm pretty much sold on the idea that digestive issues can and do appear with greater frequency alongside cases of autism. This finding now being replicated quite a few times in the peer-reviewed arena and across different geographical boundaries. I hold off from saying this is a universal issue across all autism because the data don't point to that, and universals tend to be few and far between when it comes to the autisms. Perhaps GI issues form a part of one or more particular 'types' of autism?
As per yet another quote about the Chaidez paper: "The researchers did not address the reasons why the children with autism and developmental delay experienced more GI difficulties in this study. They noted that their findings suggest that the subject warrants additional inquiry". To me this then represents the important next step in this area of investigation. We know for example, that children with autism are more likely to experience problem issues in relation to food and feeding habits (see here and here). Research is also starting to appreciate that physical activity levels are also an important area of further investigation in relation to autism (see here) which might also impact on such GI issues.
After that it starts to get a little bit more 'interesting'. Are such issues a manifestation of problems with specific food groups? Gluten, casein or something more general like carbohydrates and their metabolism (see here)? Are there other factors which might be implicated in the presentation of such GI issues, bearing in mind this could be genetic factors and possibly even more environmentally-based factors? With all the quite detailed information available to the various research groups about cohorts such as those involved in CHARGE, the possible answers are already locked in the available data.
Without giving any medical or clinical advice, if readers need any further information about this topic, you are directed to your healthcare provider and the various evidence-based guidance on the subject**** (open-access). The commentary from Dr Tim Buie on the Chaidez study also contains some nuggets of information which readers might find useful (see here). And if readers are so inclined, another big name in GI issues and autism - Prof. Simon Murch - is talking at the NAS 2014 Professional Conference here in the UK (see here). One to see I'd say.
* Chaidez V. et al. Gastrointestinal Problems in Children with Autism, Developmental Delays or Typical Development. J Autism Dev Disord. 2013 Nov 6. [Epub ahead of print]
** Gorrindo P. et al. Gastrointestinal dysfunction in autism: parental report, clinical evaluation, and associated factors. Autism Res. 2012 Apr;5(2):101-8.
*** Kushak RI. et al. Intestinal disaccharidase activity in patients with autism: effect of age, gender, and intestinal inflammation. Autism. 2011 May;15(3):285-94.
**** Buie T. et al. Evaluation, diagnosis, and treatment of gastrointestinal disorders in individuals with ASDs: a consensus report. Pediatrics. 2010 Jan;125 Suppl 1:S1-18.
Chaidez V, Hansen RL, & Hertz-Picciotto I (2013). Gastrointestinal Problems in Children with Autism, Developmental Delays or Typical Development. Journal of autism and developmental disorders PMID: 24193577