Background: People with autism spectrum disorder (ASD) often struggle with gastrointestinal symptoms, implicating alterations of the gut-microbiota-brain axis, which has also been linked to sensory reactivity, pain, and gastro-intestinal symptoms in ASD. To better understand the prevalence and impact of gastrointestinal symptoms among individuals with ASD, a measure is needed that adhere to the Rome IV criteria of gastrointestinal symptoms and is applicable to individuals with ASD. The Gastrointestinal Symptom Severity Scale (GSSS) is a new assessment tool designed to match this need. Methods: In a diverse sample of 265 individuals with ASD ( mean age = 9.44, SD = 4.99), we examined the psychometric properties of the GSSS, the prevalence of gastrointestinal symptoms and associations with ASD traits, sensory sensitivity, repetitive behaviors, and pain. Results: A unidimensional factor structure of the GSSS was confirmed and the measure showed good internal consistency, adequate test-retest reliability and strong convergent validity. Around a third of the participants evidenced clear difficulties with gastrointestinal symptoms and gastrointestinal symptoms were strongly associated with more pronounced ASD traits, sensory reactivity, and repetitive behaviors. Conclusions: The GSSS shows promise as a useful measure to analyze the prevalence, severity, and impact of gastro-intestinal symptoms in individuals with ASD. (c) 2024 The Author(s). Published by Elsevier Ltd on behalf of Editrice Gastroenterologica Italiana S.r.l. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ )

Background: Functional gastrointestinal disorders (FGIDs) are a set of chronic or recurrent gastrointestinal symptoms (GS) with great psychobiological complexity. The appearance of FGIDs harms quality of life and drains medical resources. Methods: Psychometric properties of the Gastrointestinal Symptom Severity Scale (GSSS) based on Rome IV criteria were examined in a sample of 1247 individuals with typical development. Observations were randomly divided into two subsets, namely, subsample 1 (n = 624) and subsample 2 (n = 623). Exploratory factor analysis (EFA) was performed with data from subsample 1, whilst confirmatory factor analysis (CFA) was performed with data from subsample 2. Internal consistency of the scale was assessed for the whole dataset according to ordinal alpha, whilst four-week reliability was measured according to the intraclass correlation coefficient (ICC). Measurement invariance as a function of sex was also examined, and discriminant–convergent validity of the GSSS was examined through hypothesis testing. Results: EFA revealed a two-factor structure with a moderate percentage of explained variance (51.3%), whilst CFA exhibited an excellent fit of the data to the model. A one-factor CFA model demonstrated an acceptable but slightly lower fit. Internal consistency was moderate and test–retest reliability was deemed adequate. Metric invariance was demonstrated as a function of sex. Hypothesis testing demonstrated strong convergent–discriminant validity with measures of sensory sensitivity, obsessive–compulsive symptoms, and pain. Conclusions: The GSSS is a tool with acceptable and promising psychometric properties when administered to neurotypical adolescents and young adults. The self-report GSSS may promote better understanding of GS involvement in the gut microbiota–brain axis in the general population.

Background: Recent studies indicate the need to examine how the gut microbiota–brain axis is implicated in pain, sensory reactivity and gastro-intestinal symptoms in autism spectrum disorder (ASD), but no scale exists that assesses all these constructs simultaneously. Methods: We created a pool of 100 items based on the real-world experience of autistic people, and a multidisciplinary team and stakeholders reduced this pool to 50 items assessing pain, sensory hypersensitivity, and sensory hyposensitivity. In the present study, we present this new assessment tool, the Pain and Sensitivity Reactivity Scale (PSRS), and examine its psychometric properties in a sample of 270 individuals with autism spectrum disorder (ASD; mean age = 9.44, SD = 4.97), of which almost half (45%) had intellectual disability (ID). Results: A factorial model of three factors (pain, hyporeactivity, and hyperreactivity) and five specific factors for sensory hypo- and hyperreactivity, respectively, fitted the data well. Good to excellent internal consistency and adequate test–retest reliability was found for most PSRS scales. Sound psychometric properties were found in individuals with and without ID. Correlations with other measures of sensory sensitivity and pain indicated sound convergent validity. Conclusions: PSRS shows promise as a reliable measure to analyze pain and sensory reactivity in autistic people regardless of whether they have ID or not. The measure overcomes several limitations of previous assessment tools and includes variables that are important for the understanding of the gut microbiota–brain axis in ASD.