Recently we received a question from one of our readers about a large study regarding children with autism and Gastrointestinal (GI) Issues. Please see what our Dr. Charles Cowan had to say:

Thanks for your post pointing out this most interesting and important recent study. This UC Davis/MIND Institute study is the largest study to date on gastrointestinal (GI) issues in children with Autism Spectrum Disorders (ASD). For those of you who haven’t heard of this study or read it, in brief summary the authors used data from CHARGE (CHildhood Autism Risks from Genetic and the Environment) database. This is a very large study which enrolled 1,513 participants from 2003-2011. Most participants completed a questionnaire about GI symptoms, such as diarrhea, constipation, abdominal pain, and food intolerance to compare the prevalence of these symptoms between children diagnosed with ASD, non-autism Developmental Delay (non-ASD DD) and Typical Development (TD).

GI problems have been recognized for years as highly prevalent in children with ASDs. This has prompted lots of speculation about the cause of these problems and how they are actually related to ASDs. Studies over time have varied, including one highly quoted study from the Mayo Clinic in 2009, which suggested that though the prevalence of GI problems was high in children on the spectrum the prevalence was NOT statistically higher than TD populations. Many disagreed with these results, as our collective clinical experience was that these problems were quite common. This much larger study confirms what many of us have suspected– the prevalence of a range of GI symptoms especially constipation, food selectivity and other symptoms is very high in ASD populations. In fact these problems are statistically much more prevalent than in typically developing populations.

What we learned additionally from this study is that GI problems are also highly prevalent in non-autistic developmentally delayed children, but the rates though lower are not statistically different. It should however be emphasized that not all children on the autism spectrum or with non-ASD DD have GI problems. The highest rate of problems related to food sensitivity (food restriction, picky eaters and the like). This problem affected about 30% of the population versus 4.5 % of typically developing children. Constipation was the next highest symptom affecting 15.5% of the ASD population, 15.8% of the non-ASD DD population, but only 3.5% of the TD population. Other symptoms were also prevalent to a lesser degree such as diarrhea (13%), gas and bloating (11%). Though these numbers are high, most children do not have significant GI problems.

This study also pointed out that there seems to be a strong correlation between problem behaviors and GI symptoms in both ASD and non-ASD DD children. The more severe the ASD or developmental delay was, the higher the rate and severity of problem behaviors.

So what does this study add to our understanding of ASDs?

First, that a thorough examination of GI symptoms should occur in children diagnosed with ASD and non-ASD DD. Many times these symptoms are treatable. This is especially true for constipation and gastroesophageal reflux. More difficult to understand and treat are food restriction/selectivity/sensitivity behaviors. Nevertheless, looking at and attempting to treat these symptoms may help with a range of problem behaviors.

Secondly, this study raises, as of yet, unanswered questions about why this association exists. Some have postulated that the GI problems “cause the autism” and suggest that treating the GI problems with diets, supplements and the like can effectively and substantially help autistic core symptoms (communication problems, social skill deficits and repetitive behaviors). There is nothing in this study to suggest this is true. In addition, so far, I am not aware of any study that demonstrates such GI therapies substantially affect core symptoms of autism. However, reduction of problem behaviors by treating GI problems, that may be the consequence of untreated pain, for instance, is very reasonable and will potentially improve overall functioning. These issues should always be explored with every child on the spectrum.

More work is clearly needed. The mechanisms of these GI symptoms remain mysterious. We know that the intestinal tract, is to a large extent, part of the nervous system. There are more neurons in the gut than in the spinal cord. It is plausible that the same neural mechanisms that are part of autism are also part of the motility problems in the gut.  Studying autism is like peeling an onion. There is always another layer to uncover.