Autism Spectrum Disorders (ASD) comprises a complex group of disorders of neuronal development characterized by social and communication impairment along with presence of repetitive and restrictive behaviors. Emerging evidences support the gut-brain axis and further microbiota-gut-brain axis. Elevated prevalence of gastrointestinal (GI) dysfunction in individuals with ASD suggested that targeting gut may benefit patients with ASD. Lactobacillus plantarum PS128 (PS128) was reported to be a psychobiotic in several animal studies which modulated the levels of neurotransmitters in different brain areas. The current randomized, placebo-controlled trial was conducted to investigate the psychophysiological effects of PS128 in preschool children with ASD.

Emerging evidences support the gut-brain axis and further microbiota-gut-brain axis. Elevated prevalence of gastrointestinal (GI) dysfunction in individuals with ASD suggested that targeting gut may benefit patients with ASD. Lactobacillus plantarum PS128 (PS128) was reported to be a psychobiotic in several animal studies which modulated the levels of neurotransmitters in different brain areas. The current randomized, placebo-controlled trial was conducted to investigate the psychophysiological effects of PS128 in preschool children with ASD.

Inclusion Criteria:

• Fulfill Diagnostic and Statistical Manual of Mental Disorders fifth version (DSM-V) criteria of Autism Spectrum Disorder
• Do not take any other probiotics for at least 3 weeks before and during the study period

Exclusion Criteria:

• Autistic children with other neurodevelopmental disorders or psychiatric diseases
• With a clinically significant chronic medical condition, including; anemia, brain malformations, metabolic diseases, epilepsy, organic gastrointestinal disorders (i.e. gastroesophageal reflux, food allergies, irritable bowel syndrome (IBS)) and Celiac disease
• On anti-fungal, antibiotics, special diet (i.e. gluten-free diet, casein-free diet, high-protein diet, ketogenic diet) and current use of psychiatric medications within the preceding 3 weeks were excluded
• Known allergy to probiotics

Investigators, researchers, outcome assessors, subjects and caregivers will be blinded to the randomization. A research assistant who is not involved in this trial will do the randomization by using randomly permuted blocks within the strata of two assignments, the placebo group and PS128 group with the ratio of 1:1.