Susan L. Hyman, M.D.
Professor – Department of Pediatrics, Neurodevelopmental & Behavioral Pediatrics
University of Rochester Medical Center, School of Medicine and Dentistry
Some families come into my office and tell me that they observe that their child with an Autism Spectrum Disorder (ASD) experiences behavioral change with constipation.** Many families report selective eating and express concern how a limited variety of foods their child is willing to eat might affect their health. Other families don’t associate variability in their child’s behavior with gastrointestinal (GI) symptoms until asked about other signs of discomfort. In this blog I will discuss some of the commonly asked questions I hear from families about these and other potential associations between GI symptoms and ASD.
How often do children with ASD have constipation or other gastrointestinal (GI) symptoms?
The rate of GI symptoms reported by families for their children with ASD is 20-70% depending on the definitions used and the groups studied (Mazurek et al., 2013; Mourisden et al 2013; Wang et al, 2011; Buie et al, 2010; Ibrahim et al. 2009). The two GI problems that research data consistently report occurring with greater frequency among children and youth with autism are constipation and feeding problems. Medical chart review of children and teens with ASD compared to controls in Olmstead County Minnesota identified that constipation (34% vs 18%) and food refusal (25% vs 16%) were the only two GI problems reported more commonly in the group with ASD (Ibrahim et al., 2009). Families participating in the Autism Treatment Network registry reported GI symptoms in 24% of the children; with the most common symptoms being constipation in 12% and abdominal discomfort in 11.7% (Mazurek et al., 2013). No difference in stool patterns or consistency was reported for children less than 42 months of age later diagnosed with ASD compared to controls (Sandhu et al., 2012). In this same large prospective study in the UK, children later diagnosed with ASD were reported to be more selective in their eating patterns by 15 months of age, however (Emond et al., 2012). Even less is known about the GI symptoms of adults with ASD. A longitudinal study of a registry of people with ASD in Denmark found no increase in hospital care for GI disorders compared to the general population, except for disorders of the oral cavity (including dental disease). While not statistically significant, there was the observation that GI problems may be more common among people with lower IQ (Mouridsen et al, 2013; Mouridsen et al 2010).
Why is constipation more commonly reported?
The studies of GI symptoms in children with ASD use different definitions so it is difficult to compare them. Some do not define what they consider as constipation. Some report on lifetime prevalence to date of a reported symptom, some report on symptoms within a shorter time frame, some ask about chronic symptoms. Constipation is typically defined as less than 3 stools per week and/or stools that are difficult or painful to pass. Constipation might be increased in people with ASD because of behavioral stool withholding due to stress or discomfort around having a bowel movement, decreased fluid intake, decreased consumption of fiber, decreased activity, medications used for other purposes that affect intestinal motility, or perhaps primary intestinal problems. To date the research literature has not confirmed that people with autism have abnormal motility or movement of their intestines to cause constipation (Buie et al, 2010). One study did not find an association of constipation with diet or with medication use (Gorrindo et al, 2012). The typical interventions used for constipation in children can be effective for children with ASD, (Buie 2010) so children with infrequent and difficult to pass stools should be seen by their health care provider for evaluation and management. Toolkits for families and clinicians regarding constipation management have been developed by both the American Academy of Pediatrics (published in the AAP Autism Toolkit) and the Autism Treatment Network (online publication).
Why might children with ASD have feeding problems?
Food selectivity might be related to perseveration or repetitive behaviors, discomfort related to food allergies/intolerances, discomfort related to gastrointestinal reflux, sensory differences, or other behavioral influences. Future postings will discuss feeding behaviors further including behavioral and nutritional suggestions. While there is not documentation that children with ASD have an increased rate of gastrointestinal reflux, this is a common medical problem and needs to be considered if a child has food refusal, vomiting after meals, belching after meals or signs of chest or abdomen discomfort.
Does the food itself cause GI symptoms?
Specific foods can cause GI symptoms based on allergy, food intolerance, or medical conditions that are not specific to ASD. An example is the excess consumption of juice that results in “toddlers diarrhea” in children with and without autism. Other common medical problems like lactose intolerance, the inability to digest milk sugars, might result in abdominal pain or diarrhea with exposure to milk products. Lactose intolerance runs in families. It can occur temporarily after a viral diarrheal illness or antibiotic use. If a family or patient identifies discomfort or GI symptoms related to a specific food, further evaluation by an allergist or gastroenterologist may be necessary. If a food group like dairy products are eliminated on a trial basis, other products need to be substituted that can provide the nutrients that would otherwise be found in that food.
What about gluten?
GI disorders that occur in other people also occur in people with ASD. We do not have evidence at this time that celiac disease is more common among children with ASD then among other children. Although some immune response to gluten that is different from that seen in celiac disease might be found more frequently in children with ASD (Lau et al, 2013). Celiac disease is an immunologic intolerance to the peptide gluten found in food products containing barley, rye and wheat. The population prevalence of celiac disease is about 1:100, which is fairly common, so celiac disease should be considered in the work up of GI symptoms or poor growth in children with and without ASD. There is now a blood test that serves as first level test for celiac disease. Many families elect a trial of removal of gluten and/or casein from their child’s diet. The reason they do this is not because of food allergy or celiac disease and is based on individual observations relating diet and behavior. Diet and ASD will also be discussed in future blogs in this series.
Can GI discomfort lead to behavioral symptoms?
Since many individuals with ASD do not report pain in a typical fashion or do not have the language to report discomfort, a change in behavior may be the only clue the family or clinician has that a painful condition is present. GI problems like gastrointestinal reflux or constipation benefit from conventional medical treatment. The family and clinician must be alert for symptoms like belching after meals and air swallowing in addition to the more classic symptoms of gastrointestinal reflux of vomiting after meals or report of heartburn. Painful conditions in general may lead to behavioral change in people with ASD, so dental pain, headaches, minor injuries, and other general medical conditions need to be considered with an acute change in behavior. GI symptoms have been associated with challenging behaviors like opposition, sleep problems, and food selectivity (Maennur et al, 2012 ).
Isn’t anxiety associated with GI symptoms?
Anxiety is associated with abdominal pain in children and youth with and without ASD. An association between GI symptoms, anxiety and reported sensory symptoms was identified in children participating in the Autism Treatment Network (Mazurek et al, 2013). Anxiety may be more common among people with ASD for biological reasons, because of problems with state dysregulation, or perhaps because they cannot predict what will happen in the environment. Research needs to be done to determine if treatment of the anxiety improves GI symptoms or if treatment of the GI symptoms improves anxiety.
Are the bacteria and other microbes in the intestines associated with GI symptoms?
There is a lot of interest in the role of the bacteria and yeasts that live in the intestine that aide in both absorption of nutrients and in normal GI functioning. Current research studies are investigating if there are differences in the patterns of intestinal bacteria in children with ASD (Gondalia et al., 2012; Williams et al, 2011). Whether probiotic supplements provide benefit to people taking a balanced diet requires further research. They are typically without side effects.
Has research demonstrated other differences in the GI tract in people with ASD?
There are several hypotheses about GI function in people with ASD that have conflicting evidence. Some studies are not of the quality to allow scientific conclusions to be drawn. Theories that are as yet unproven include the hypothesis that people with autism have an alteration in the production of digestive enzymes (Williams et al, 2011, Munasingh et al, 2010), the hypothesis that there is altered microscopic appearance to the intestinal lining (Chen et al, 2011; McDonald, 2007) and the hypothesis that there is a “leaky gut” that allows abnormal absorption of nutrients that produce behavioral change in people with ASD (Buie, 2010). Because the development of intestine and brain are both directed by genes early in fetal life, it is plausible that future research might find genetic or environmental influences that impact the development of both brain and gut.
In summary, when people with ASD have GI symptoms they need to be evaluated for the common –and if indicated, uncommon – conditions that produce GI symptoms in other people including anxiety. With acute behavioral change, all sources of potential discomfort need to be considered. Children with ASD have increased rates of constipation and feeding problems compared to other children. Clinical and basic research is required to answer the many questions related to the specific causes and treatments for the GI symptoms of individuals with ASD.
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