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

August 27, 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

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
50

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • 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
      • Naples, Naples, Italy, 80131
        • Department of Traslational Medical Science - University of Naples Federico II

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

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
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

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
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). The primary outcome was week-16 response, defined a priori as a reduction of more than 4 points in Gastrointestinal Severity Index (GSI) score.
At 16 weeks of treatment

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
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

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
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)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
January 1, 2023

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
April 30, 2026

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
April 30, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 9, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
January 7, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
January 15, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
August 31, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 27, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
August 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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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