A Descriptive Review on the Prevalence of Gastrointestinal Disturbances and Their Multiple Associations in Autism Spectrum Disorder

Abstract

Background and Objectives: Gastrointestinal disturbances have been frequently, but not unanimously, reported in autism spectrum disorder (ASD) individuals. Thus, digestive symptoms, such as constipation, diarrhea, abdominal bloating, and pain have been reported to correlate to the various maladaptive behaviors in ASD children, such as irritability, social withdrawal, stereotypy, hyperactivity, and even language regression. In this context, the present study provides an overview on the prevalence of the gastrointestinal (GI) disorders in ASD and the correlation between these and ASD symptoms and comorbidities and subsequently discusses the metabolic and microbiome factors underlying the effects of GI disorders in ASD. Materials and Methods: For our analysis of GI symptoms in children with ASD, we have searched peer-reviewed journals from 2005 to 2017 in PubMed databases that addressed the specificity of GI symptoms in ASD and included correlations of GI and ASD symptoms. The criteria for inclusion were clear quantitative mentioning of GI modifications, GI symptoms correlation with specific ASD symptoms or comorbidities, an appropriate methodology for defining ASD, and larger size samples. For this topic, only studies on human patients and original research were considered. A subsequent search in PubMed databases in journals from 2000 to 2017 we analyzed 13 articles on the mechanisms underlying the impact of GI dysfunctions in ASD, including gut microbial dysbiosis, immune reactivity, genetics, and altered neurotransmitters on the gut–brain axis. Results: In the 18 original research studies that we selected out of an initial 327 studies, despite the different methodology, a predominant 83% highlighted the increased prevalence of GI symptoms in ASD patients. Constipation was most frequently cited, appearing in 12 of the studies (80%), followed by diarrhea reports in eight studies (53%). The association between cognitive and behavioral deficits and GI disorders was suggested in certain groups of ASD individuals. Conclusion: The evidence presented so far by numerous studies seems to indicate that GI dysfunctions are of particular relevance in ASD, underlined by various abnormalities along the nervous connections between the central nervous system and the gut, such as impaired parasympathetic activity and increased endocrine stress response. Sufficiently large size samples and standardized methodology are required for future studies to clarify the complex interactions between GI disturbances and ASD symptoms.

Fundamental Role of Neurochemicals Aberration in the Pathogenesis of Autism Spectrum Disorders

“…Furthermore, most of the autistic children in the present study had gastrointestinal (GI) problems; 80% in atypical autism and 86.7% in childhood autism versus 20% in the control group. These findings are paralleled to the recent report by Lefter et al [23] who stated that the increased prevalence of GI symptoms in ASD patients indicating that GI dysfunctions are of particular relevance in ASD. These various GI manifestations are related to the autonomous nervous system affecting the parasympathetic tone and stress responsiveness as well as abnormal dynamics of neurohormones such as serotonin or GABA.…”

<p>Bridging the Gap Between Physical Health and Autism Spectrum Disorder</p>

“…GI disorders are significantly overrepresented in ASD compared with the general population. 119 Individuals with ASD present with frequent functional issues of diarrhoea, constipation, and gastroesophageal reflux alongside higher rates of inflammatory bowel diseases. 120 Various other clinical findings appear to be overrepresented in ASD, including increased intestinal permeability, various digestive enzyme deficiencies and bacterial dysbiosis.…”

Minireview Exploring the Biological Cycle of Vitamin B3 and Its Influence on Oxidative Stress: Further Molecular and Clinical Aspects

“…Considering the myriad functions fulfilled by the gut microflora [ 131 ] and the close link between the brain [ 25 , 132 ] and digestive tract [ 33 , 133 ], there have been relatively few reports aiming to demonstrate how OS gradually induces dysbiosis. This section focuses on the studies and hypotheseses that clearly demonstrate how OS disrupts host eubiosis [ 134 ].…”