Functional gastrointestinal (GI) symptoms have been frequently reported in children with autism spectrum disorders (ASD). The term ‘functional’ refers to the absence of structural abnormalities in the gut that can be identified by blood, radiographic or endoscopic tests. Functional GI symptoms are also common in the general population and account for a major portion of visits to gastroenterology and primary care practices. Abnormalities in the neural regulation of gut function and sensation have been implicated in the development of these complaints.

A review of previous studies suggests that GI symptoms are more common in children with ASD than in neurotypical children. However a major barrier to integrating the ASD studies on GI symptoms with those conducted in the general population has been that the instruments used to assess functional GI symptoms in ASD differed from the Rome III process, which is the current international standard by which functional GI disorders are diagnosed.

Alterations in the composition of resident gut microbial communities have been reported for an increasing number of human disorders, including ASD and functional GI disorders. In order to assess the associations between ASD phenotype, functional GI disorders and fecal microbiota, Ellen Li and her colleagues at Stony Brook University recruited individuals with ASD and neurotypical siblings (7-14 years of age) from the Simons Simplex Community through the Interactive Autism Network (SSC@IAN) to participate in a study collecting fecal samples and metadata related to functional GI disorders and diet.

Li’s group found that 25 of 59 ASD children and 13 of 44 neurotypical siblings met Rome III criteria for at least one functional GI disorder. Functional constipation was more prevalent in ASD children (17 of 59) compared with neurotypical siblings (6 of 44, p = 0.035). Problem emotions and behaviors, when assessed by the parents using the Child Behavior Checklist, were increased in neurotypical siblings with functional GI disorders to the same extent as in ASD children (with or without functional GI disorders), compared with neurotypical siblings without functional GI disorders.

In addition, Li and her colleagues detected an increased amount of one bacterial subgroup in ASD children with functional GI disorders. However, detailed inspection of the dietary diaries raised the possibility that this increase was linked to consumption of chia seeds in ASD children with functional GI disorders.