Probiotics for Autism Spectrum Disorders: a Randomized Controlled Trial (The PASD Study) (PASD)

January 7, 2026 updated by: Roberto Berni Canani, MD, PhD, Federico II University
Autism spectrum disorders (ASD) are a group of severe neurodevelopmental conditions characterized by impaired communication and social interaction, as well as repetitive/stereotyped behaviors deriving from a combination of genetic and environmental factors. The ASD diagnosis rates increased dramatically over the past number of decades. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) describes a worldwide prevalence of approximately 1%. The prevalence of ASD is 1 in 59 individuals in the US reported by the Centers for Disease Control and Prevention. According to the latest data from the Italian National Observatory for ASD, the actual prevalence in Italy is about 1/77 for children aged between 7 and 9 years, with a 4.4 times higher prevalence in male. The origin of ASD is still largely undefined. It has been hypothesized a possible role for the influence of early life alteration of gut microbiome (GM). We demonstrated an imbalance in Bacteroidetes and Firmicutes phyla with a decrease in Bacteroidetes/Firmicutes ratio in the GM of pediatric patients affected by ASD. Similar data have been observed by others. Data from ASD animal model confirm the presence of GM dysbiosis with significant correlation with behavioral, gastrointestinal and immunologic alterations. Altogether these data support the hypothesis that GM dysbiosis could be involved in the ASD pathogenesis. The ASD children present an increased prevalence of functional gastrointestinal disorders (FGIDs), mainly chronic constipation, functional diarrhea, and irritable bowel syndrome (IBS). A role for GM has been suggested also for these conditions. The presence of these disorders negatively influence the disease severity and the parental quality of life of ASD children. Starting from all these considerations GM is becoming a possible target of intervention for pediatric ASD. Probiotics are one of the most investigated strategy for a beneficial modulation of GM. Probiotics are commonly defined as live microorganisms which when ingested in adequate amounts confer a beneficial effect on the host. The most used probiotics in the pediatric age are Saccharomyces and Lactobacillus strains including Lactobacillus rhamnosus GG (LGG). Data report a beneficial influence elicited by LGG on GM structure and function. This probiotic resulted also effective in treating FGIDs patients. Preliminary evidence suggest the potential efficacy of probiotics for FGIDs treatment in ASD children. Altogether these evidence strongly support the hypothesis that LGG could exert a beneficial action in ASD children. The purpose of this study is to evaluate the therapeutic efficacy of LGG on FGIDs in ASD children.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Italy
      • Naples, Italy, 80131
        • Recruiting
        • Department of Traslational Medical Science - University of Naples Federico II
        • Contact:
          • Roberto Berni Canani, MD, PhD
          • Phone Number: 0817462680
          • Email: berni@unina.it

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • children aged 4-12 years
  • children of both sex
  • children with a sure diagnosis of ASD and presence of FGIDs with a GSI ≥7 from at least 3 months.

Exclusion Criteria:

  • children aged <4 or >12 years
  • uncertain ASD and/or FGIDs diagnosis
  • FGIDs duration lasting <3 months
  • concomitant presence of other chronic conditions (adverse food reactions; genetic and metabolic disorders; malformations of GI, respiratory or urinary tract; neurologic diseases; immunodeficiencies; diabetes; cardiovascular diseases; autoimmune diseases; chronic infections; chronic respiratory, GI or urinary tract diseases; obesity; tumors; malnutrition).
  • use of antibiotics and/or pre-/pro-/ synbiotics during the 6 months prior to enrolment
  • participation into other clinical trials during the last 12 months.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Placebo Comparator: Placebo
Other: Placebo
Placebo
Experimental: Probiotic
Lactobacillus rhamnosus GG
Other: Lactobacillus rhamnosus GG
Lactobacillus rhamnosus GG

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Functional gastrointestinal disorders (FGIDs) severity
Time Frame: At 16 weeks of treatment
Severity index of gastrointestinal symptoms (GI Severity Index, GSI) - Minimum Score: 0 (Indicates absence of gastrointestinal symptoms or optimal bowel regularity) Maximum Score: 17 (Represents the highest severity of symptoms reported in the questionnaire)
At 16 weeks of treatment

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Kinetics of Lactobacillus rhamnosus GG (LGG)
Time Frame: At baseline and at 4 weeks, 8 weeks and 12 weeks of treatment
Using the GI Severity Index (GSI) - Minimum Score: 0 (Indicates absence of gastrointestinal symptoms or optimal bowel regularity) Maximum Score: 17 (Represents the highest severity of symptoms reported in the questionnaire)
At baseline and at 4 weeks, 8 weeks and 12 weeks of treatment
Duration of the LGG impact on FGIDs
Time Frame: At baseline and at 4 weeks and 12 weeks from the end of treatment
Changes in the GSI - Minimum Score: 0 (Indicates absence of gastrointestinal symptoms or optimal bowel regularity) Maximum Score: 17 (Represents the highest severity of symptoms reported in the questionnaire)
At baseline and at 4 weeks and 12 weeks from the end of treatment
Gut Microbiome (GM) composition
Time Frame: At baseline and at 16 weeks of treatment
Shotgun metagenomics analysis
At baseline and at 16 weeks of treatment
GM function: fecal short chain fatty acids (SCFAs) levels
Time Frame: At baseline and at 16 weeks of treatment
Gas chromatograph(GC)-mass spectrometry (MS) analysis
At baseline and at 16 weeks of treatment
ASD children behavior
Time Frame: At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Aberrant Behavior Checklist (ABC) questionnaire - Minimum Score: 0 (Indicates the complete absence of aberrant or problematic behaviors in the assessed areas, e.g., aggression, social withdrawal, stereotypies, etc.) Maximum Score: 174 (Represents the highest severity and frequency of problematic behaviors reported in the test. All listed aberrant behaviors-such as self-injury, severe hyperactivity, complete social withdrawal, and repetitive speech-are present at maximum intensity.)
At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Parental quality of life
Time Frame: At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
EUROHIS QOL-8 questionnaire - Minimum Score: 8 (Indicates the lowest level of satisfaction and quality of life) Maximum Score: 40 (Indicates the highest level of satisfaction and quality of life)
At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Body weight
Time Frame: At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Body weight will be evaluated in kilograms
At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Height
Time Frame: At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Body weight will be evaluated in cm
At baseline, at 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
Infectious diseases
Time Frame: At 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment
It will be assessed the number of infectious episodes, type of infectious diseases, need for drugs
At 4 weeks, at 8 weeks, at 12 weeks and at 16 weeks of treatment, and at 4 weeks and 12 weeks from the end of treatment

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Federico II University

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 1, 2023

Primary Completion (Estimated)

March 1, 2026

Study Completion (Estimated)

March 1, 2026

Study Registration Dates

First Submitted

December 9, 2025

First Submitted That Met QC Criteria

January 7, 2026

First Posted (Actual)

January 15, 2026

Study Record Updates

Last Update Posted (Actual)

January 15, 2026

Last Update Submitted That Met QC Criteria

January 7, 2026

Last Verified

October 1, 2025

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 38/2023

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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