Autism and Gastrointestinal symptoms: two new studies
Posted Jul 28 2009 10:31pm
Autism and poop. You hear those two words in the same sentence a lot on the net. People have been asking for studies on whether autistics have a higher incidence of gastrointestinal (GI) problems for a long time. Well, two papers came out in the last week with answers…and many parents are not happy.
The Bristol group’s study came out last week. Given that the Mayo Clinic study was on the way, I figured I’d wait and blog them both at the same time. Actually, I considered not blogging them at all. These papers are more nails in the coffin for Andrew Wakefield’s hypothesis that MMR causes “autistic enterocolitis” and the belief by many that this drove much of the “autism epidemic”. But, tired as that story is, the question of whether autistics have GI problems at a higher rate is important and worth discussing.
The Bristol study has free pdf access. Not so the Mayo Clinic study: abstract only, but I have a copy. Rather than go through the studies in detail (if you are that interested you will likely read the paper for yourself), let’s just look at the results and conclusions sections of the abstracts:
Results: Comparison of the ASD and control group during the first 3.5 years of life showed no major differences in stool colour or consistency, or in frequency of diarrhoea, constipation, bloody stools or abdominal pain. The ASD children had similar stool frequency up to 18 months, but there was a trend for ASD children to pass more stools at 30 months (OR 3.73, 95% CI 1.11 to 12.6; p=0.004) and at 42 months (OR 6.46, 95% CI 1.83 to 22.7; p,0.001), although only three children passed more than 4 stools/day. Repeating the analysis on only those cases diagnosed as having classical childhood autism resulted in very similar findings.
Conclusions: During the first 42 months of life, ASD children had a stool pattern that was very similar to that of other children, apart from a slight increase in stool frequency at 30 and 42 months. There were no symptoms to support the hypothesis that ASD children had enterocolitis.
RESULTS: Subjects were followed to median ages of 18.2 (case subjects) and 18.7 (control subjects) years. Significant differences between autism case and control subjects were identified in the cumulative incidence of constipation (33.9% vs 17.6%) and feeding issues/food selectivity (24.5% vs 16.1). No significant associations were found between autism case status and overall incidence of gastrointestinal symptoms or any other gastrointestinal symptom category.
CONCLUSIONS: As constipation and feeding issues/food selectivity often have a behavioral etiology, data suggest that a neurobehavioral rather than a primary organic gastrointestinal etiology may account for the higher incidence of these gastrointestinal symptoms in children with autism.
Or, to put in a single sentence: there is no evidence that children with autism have GI problems at a greater rate than the general public.
How about repeating that with emphasis: there is no evidence that children with autism have GI problems at a greater rate than the general public. They are not saying that there are no children with autism and GI issues. Quite the contrary. You wouldn’t know that to read some comments on the internet about these studies.
I’m a little surprised by these results. No, I don’t think that Wakefield was right. But, I wouldn’t be surprised if children with autism have other medical concerns at higher rates. Also, there were two abstracts from IMFAR 2008 that stuck in the back of my mind.
In the first, a team from the University of Connecticut presented a study suggesting that GI issues may be more common in children with children with ASD ’s (but at a similar rate to children with other developmental delays).
Conclusions: In this sample of young community-based children with ASDs and other developmental delays, no significant group differences in parentally reported feeding problems and gastrointestinal symptoms were found at age two or at age four. Most published research has been conducted at specialty GI or DD/ASD clinics with older children. The results of this study suggest that their findings may not be applicable to young children or to children evaluated in community settings. While GI problems may be increased in children with developmental disorders, we found no evidence that they were specific to autism spectrum disorders.
The second abstract (which later became a paper that was discussed on this blog): David Mandell’s group presented a paper suggesting that a significant fraction of adults hospitalized with schizophrenia diagnoses might actually have autism:
Their IMFAR presentation (and later published paper) showed an increased number of GI problems in their adult group. 36% of their adults had GI problems vs. 23% of the general psychiatric hospital population.
Unfortunately, these latest studies are getting the usual “online-autism-parents” community welcome. It follows the same pattern as vaccine/autism research:
a) Ask for studies to be done b) Studies are done c) Disagree with the data d) try to slime the authors
Is it a surprise to anyone that some researchers have opted out of working on autism?
(note: minor edits were made shortly after publishing this article)