I should perhaps make a distinction at this initial point between the two types of GI involvement postulated in autism. On the one hand we have a potential association between some cases of autism and GI disease - things like variants of inflammatory bowel disease, coeliac disease, etc. On the other hand we have the association with functional bowel problems - things like constipation, diarrhea, bloating. Both types of GI disorder are linked to each other and both have been linked to autism to varying degrees, generating a considerable body of research literature in the process. I have touched upon GI disease co-morbidity in a few posts (most notably here and here). For this post I am focusing on the functional bowel patterns and symptoms in light of this recently published study following other independent research.
Before proceeding I will provide you with some information on constipation (prevalence: 5-30%) and diarrhea (prevalence: ???) with particular reference to the pediatric population. The prevalence figures for constipation should be the standard that should be borne in mind when looking at the data subsequently presented in this post. OK. The study in question is from the MIND Institute by Wang and colleagues, and looked at the prevalence of functional bowel problems in autism. The details: the parents/primary caregivers of 589 people with autism were interviewed and medical history data extracted. Data for 163 siblings (unaffected by autism) were also captured. Compared with siblings, parent reports detailed significantly more functional GI problems in the autism group (42% vs. 12%) (p<0.001). Constipation and diarrhea were the most commonly cited problems and having more severe autism was associated with a higher risk of presenting with GI problems.
Bearing in mind that this study was based on retrospective recall and relied on non-specialist testimony, there was a degree of overlap from the findings and other work in this area (a sample of which is here and here) although balanced with some disparity also (here and here). There are a few points we can draw from this collected information.
- Allowing for differences in the way that such functional bowel problems are described and reported (by who, using what criteria, compared against who, etc), a diagnosis of autism does not seem to confer any protection against co-morbid functional bowel problems, at least to the same extent that they occur in age-matched populations. Whether there is any effect from gender remains to be seen.
- There is some evidence for functional bowel problems to be present more frequently in some cases of autism over others also being moderated by autism severity. At the present time however there are additional co-morbidities attached to autism (such as learning disability) that could at least partially account for results.
- In amongst the various investigations on functional bowel problems, there are only a small number of studies looking at the various reasons why such functional bowel problems could be present. I tend to cite this study by Afzal and colleagues quite a bit, simply because they suggested that milk consumption was the strongest predictor of constipation in their group. Are there other factors such as quality of diet, water intake, medication or other environmental effects which could also affect presentation?
Before I end this post, I would briefly like to touch upon the thorny issue of treatment for functional bowel problems co-occurring in autism. I say this is a thorny issue because quite a few people I have talked to down the years have not had a great experience when trying to get theirs or their child's functional bowel symptoms examined and treated properly despite some formal guidance being in place.
I am not assigning any blame and do not wish to offend anyone involved in such treatments, who do sterling work. The problem of treatment seems to exist for many reasons: low numbers of suitably qualified professionals (particularly pediatric gastroenterologists), a continued state of 'not-knowing' when it comes to autism and functional bowel issues (despite available guidance) and also perhaps other factors.
I would like to think that here in the UK, with the commencement of the NICE guidelines on autism, we will see some credit given to functional bowel problems as a potential co-morbidity to autism. Also hopefully not too far behind, some authoritative research on strategies for alleviating such problems specifically with autism in mind, and recognition of the pain and suffering that they can potentially cause.