Digestive system disorders, referred to as gastrointestinal (GI) dysfunction, are among the most commonly associated disorders of ASD. They were found in more than half of Slovak children with ASD, foreign studies show an incidence of up to 70 percent.

Digestive problems are of various natures, the most common problem is chronic constipation (stool less than once every 3 days), bulky stools, emptying can be accompanied by pain and crying. Children sometimes consciously hold their stools just to avoid pain. Other children suffer from frequent diarrhea, bloating and abdominal pain. Gastroesophageal reflux may occur, which is characterized by recurrent vomiting. Sometimes, however, reflux is asymptomatic, but it causes the child pain that is manifested by impaired behavior.

The causes of the more frequent occurrence of gastrointestinal dysfunction in ASD are only partially elucidated; it is assumed that it is the interaction of several factors. New research indicates a significant effect of intestinal microbiota. It consists of more than 1000 different microorganisms that survive naturally in the digestive system and favorably affect the function of the human body. Differences in the composition of the intestinal microbiota (dysbiosis) have been found in people with ASD. The proportion of individual bacteria has changed, pathogenic microorganisms are present in a larger number, which disrupts the proper function of the digestive system. Mild but chronic low-grade inflammation in the digestive tract may contribute to digestive problems. Causes of digestive problems also include peculiarities in the eating habits of children with autism, food intolerances and allergies.

Significant forms of autistic manifestations – repetitive behavior or impaired social communication – were found in children with ASD who had digestive problems. Problem behaviors, such as self-harm, aggression, or anxiety, have also been shown to be more common than in children with ASD who did not have GI problems. This connection is explained by the so-called “Gut-brain axis”, the connection between the gut and the brain through nerve signals or blood-borne substances. Different microbiota, inflammatory process and increased intestinal permeability cause the transmission of abnormal signals to the brain, adversely affect its function and contribute to the development of behavioral manifestations of autism.

Manifestations of digestive problems in children with ASD may not be usual. They can manifest themselves in the appearance or escalation of problematic behavior that is not clearly related to any evoking stimulus.

As part of comprehensive care, a child with ASD should be examined by a specialist – gastroenterologist, who will recommend appropriate therapy if necessary. Treatment depends on the findings and the type of disorder. In some disorders, it is possible to affect the intestinal microbiota with probiotics. Studies suggest a beneficial effect of probiotics not only on digestive functions but also on the behavior of children with ASD. However, it is not yet clear which probiotics bring the greatest benefit in regards to ASD.

Nutrition adjustment is also part of the treatment. In case of constipation, it is recommended to include foods rich in fiber (fruits, vegetables, legumes, whole-meal bread) in the child’s diet; on the contrary, in case of loose stools and bloating, it is suitable to provide non-irritating food without residues such as kernels or skins. In food allergies and intolerances, foods to which the child is allergic or which cause intolerance are excluded from the diet. Due to dietary peculiarities, the transition to diet and adherence to dietary principles can be problematic.