Effect of Probiotics on GI Symptom Management in Autism Spectrum Disorder: A Systematic Review and Meta-Analysis of Clinical Trials

Autism spectrum disorder has increased worldwide over the past few decades. Medical comorbidities are common in patients with ASD, with gastrointestinal (GI) diseases being especially common. Involvement of the gut-brain axis that communicates between the enteric and central nervous systems has been confirmed by several studies that have reported abnormal microbiota profiles in ASD subjects. In this review, a systematic database search was conducted. Six trials were included in the subgroup analysis that compared probiotic therapy with single or multiple strains to a placebo with respect to gastrointestinal severity index. The pooled effect size model revealed a slight decrease in gastrointestinal symptoms that favored probiotic supplementation (SMD = -0.189; 95% CI = -0.398 to 0.020; Z = -1.773, p = 0.07; I2 = 39.4%). There was a moderate level of heterogeneity among the included studies. Additionally, the effects of single-strain and multiple-strain probiotic formulations were compared to their respective placebo groups using subgroup analysis. The results demonstrated that single-strain probiotic medication reduced gastrointestinal symptoms when compared to the placebo group. However, there was no statistically significant difference between multiple-strain probiotic therapy and a placebo. To accurately establish the therapeutic effects of probiotics on ASD, more randomized, double-blind, placebo-controlled studies are required.