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The predominant data on gastrointestinal problems in autism
Most studies of autism/autistic spectrum disorders (link to Autism Society) have documented an increased prevalence (9% to 90%) of gastrointestinal symptoms. The difference may relate to different design and different definitions of clinical criteria studied in addition to the subsets of cohorts/ settings analyzed e.g. clinic based versus population based studies.
The negative data
Despite the overwhelming observations by families and scientific there remains a small section of scientific community that has questioned such a difference based on minority of literature (Kuddo T et al, Black C et al).
In fact, an editorial in the journal Pediatrics (Gilger et al) stated with confidence that “putting to rest the nagging suggestion that there exists a link between autism and gastrointestinal disease”. However, many experts have argued against putting too much stock in this.
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The categorical statement by Gilger et al. was largely based on single study from Mayo Clinic (Ibrahim et al) that not only had numerous serious methodological flaws but the design itself does not even come close to the gold standard to scientific evidence of prospective studies especially randomized, double blind and controlled. The drawbacks of Ibrahim study included:
- Retrospective analysis of medical records
- Small sample size
- No gastrointestinal and/or nutritional intervention
- Did not require a specific clinical diagnosis of autism or ASD but was based on a research diagnosis thus potentially including any/all behavioral problems related subjects diluting the autistic effect.
- Even all its caveats documented an increase in constipation and food intolerance in autistic kids but dismissed that as behavioral issue or possible related to side-effects of medications and no link to autism itself.
In fact, a subsequent review from Harvard University (Harvard Mental Health Letter 2010) commented that “other research suggests that children with ASDs also frequently experience abdominal pain (with or without diarrhea) stool leakage (encopresis), abdominal bloating, and gastroesophageal reflux disease”.
A newer, larger, better controlled study using clinical diagnosis of autism/ASD:
- A more recent and in my opinion better/definitive study utilizing unaffected siblings as controls also directly contradicts the naysayers (Wang et al. 2011 from University of California, Davis, CA).
- Included subjects wherein at least 2 members of family had autism/ASD
- Unaffected siblings used as controls
- Structured medical history interviews by pediatric neurologist
- ASD classified into Full autism, Almost autism and Spectrum
- Subject n=589 autism/Autistic spectrum disorder
- Control n= 163 unaffected siblings
Results of Wang study
- 42% of autism/ASD subjects had GI problems as compared to 12% among controls.
- There was significantly more constipation (20% v 4% in controls) , diarrhea 919% v 2% in controls) and other GI problems whereas the prevalence of gastroesophageal reflux was similar.
- Prevalence of GI problems in Spectrum group was similar to controls.
- After adjusting for confounding variables like age, gender and current medications, the subjects with full autism and Almost Autism had 14.3 and 5.2 times greater odds of having gastrointestinal problems.
- Increased severity of autism was associated with increased odds of
having GI symptoms.
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So what are your thoughts on prevalence of GI problems in autism/ASD. Is it increased or no big deal? Please sure your thoughts. 
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