Gastrointestinal symptoms in autism spectrum disorder: a meta-analysis.

BACKGROUND In pediatric settings, parents often raise concerns about possible gastrointestinal (GI) symptoms in autism spectrum disorder (ASD), yet the specificity of these concerns are not well studied. OBJECTIVE To conduct a meta-analysis of research investigating GI symptoms among children with ASD. METHODS We searched Medline, PsycINFO, and PubMed databases (1980-2012) in peer-reviewed journals. Analysis involved studies with a comparison group presenting quantitative data on GI symptoms using combinations of terms for ASD and GI indicators. The systematic search yielded 15 studies. We calculated effect sizes and 95% confidence intervals (CIs) using a random-effects model. RESULTS Children with ASD experience significantly more general GI symptoms than comparison groups, with a standardized mean difference of 0.82 (0.24) and a corresponding odds ratio (OR) of 4.42 (95% CI, 1.90-10.28). Analysis also indicated higher rates of diarrhea (OR, 3.63; 95% CI, 1.82-7.23), constipation (OR, 3.86; 95% CI, 2.23-6.71), and abdominal pain (OR, 2.45; 95% CI, 1.19-5.07). CONCLUSIONS Results indicate greater prevalence of GI symptoms among children with ASD compared with control children. Identified studies involved high methodological variability and lack of comprehensive data prohibited analysis of GI pathophysiologies (eg, gastroesophageal reflux) typically associated with organic etiologies, limiting conclusions about the underpinnings of the observed association. Future research must address critical questions about the causes and long-term impact of GI symptoms in ASD. Such analyses will require more systematic research and clinical activities, including improved diagnostic screening, standardized assessment, and exploration of potential moderators (eg, dietary restrictions).