Improving ADHD Symptoms and Quality of Life Through Diet

NCT07376746 | Not Yet Recruiting

• 1 other identifier: APC199
• Study Type: interventional
• Target: 200
• Locations: 1 country
• Sites: 1

Brief Summary

The goal of this randomised controlled trial is to evaluate whether a specific dietary intervention can reduce core symptoms of Attention-Deficit/Hyperactivity Disorder (ADHD) in adults aged 18 to 50 years. The study also aims to understand how changes in diet may influence quality of life, neurocognitive function, and gut-brain signaling through the microbiota. The main questions it aims to answer are:

1. 1.Does a high-fiber, fermented food-based diet reduce ADHD core symptoms over a 12-week period, as measured by the Conners' Adult ADHD Rating Scale (CAARS)?
2. 2.Does the diet improve neurocognitive function, mood, food reward, individual goals, and other quality-of-life outcomes?
3. 3.How does the diet affect gut microbial composition, inflammation, and stress-related biomarkers?
4. 4.Is the diet well-accepted and feasible to follow?
5. 5.Complete six study visits over a 24-week period (screening, baseline, weeks 4, 8, 12, and optional follow-up at week 24).
6. 6.Be randomly assigned to one of two dietary groups after baseline assessments.
7. 7.Provide stool, saliva, urine, and blood samples at multiple timepoints.
8. 8.Undergo cognitive testing and EEG recording to assess brain function.
9. 9.Wear a wristband to track sleep and activity patterns.
10. 10.Use a nutrition app to log dietary intake and receive weekly dietary support.
11. 11.Complete validated questionnaires on ADHD symptoms, mood, eating behavior, gastrointestinal health, sleep, and lifestyle factors. Feasibility and acceptability of following the diet will also be self-reported.

Conditions

ADHD

Keywords

Psychobiotic diet; ADHD; Fermented foods; Gut-Brain Axis; Dietary fibre

Outcome Measures

Primary Outcomes (1)

• Change in ADHD core symptoms

  Change in ADHD core symptoms from baseline to the end of diet (12 weeks) measured by Conner's ADHD rating scale total score (CAARS). The CAARS Total ADHD Symptoms score ranges approximately from 0 to 100, with higher scores indicating greater ADHD symptom severity (worse outcome).

  From baseline to 12 weeks

Secondary Outcomes (1)

• Change in neurocognitive function and mood, and other secondary domains

  From baseline to 12 weeks

Other Outcomes (1)

• Tertiary Outcomes

  From baseline to 12 weeks (end of dietary intervention)

Study Arms (4)

No ADHD/Combined Diet

EXPERIMENTAL

Participants without ADHD will receive a combined diet (fermented foods and high fiber)

Other: Combined diet

No ADHD/Control diet

NO INTERVENTION

Participants without ADHD will receive dietary education based on the healthy eating guidelines provided by the Health Service Executive (HSE).

ADHD/Control diet

NO INTERVENTION

Participants with ADHD will receive dietary education based on the healthy eating guidelines provided by the Health Service Executive (HSE).

ADHD/Combined diet

EXPERIMENTAL

Participants with ADHD will receive a combined diet (fermented foods and high fiber)

Other: Combined diet

Interventions

Combined diet OTHER

Participants will receive dietary education to increase their fibre intake to 25-30g/day and include 3 to 4 portions of fermented foods to their normal diet.

ADHD/Combined diet; No ADHD/Combined Diet

Eligibility Criteria

• Age: 18 Years - 50 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• Be able to give written informed consent
• Should be stable for 4 weeks on psychopharmacological medication or without medication
• Should have an established diagnosis of ADHD or ADD as the main mental disorder diagnosis. This will be validated by the ADHD diagnostic criteria after DSM-5, with the DIVA interview.
• Aged 18-50 years
• Fluency in English language
• Be able to give written informed consent
• Should be stable for 4 weeks on any medication for physical health or without medication
• Should not currently taking psychopharmacological medicine or discontinued psychopharmacological medicine in the past 6 months (due to relapse risk)
• Should NOT have an established diagnosis or clinical symptoms of ADHD or ADD. This will be validated using with the ASRS-6 (\< 4)
• Should not have a diagnosis of ASD as indicated by self-report.
• Not have current, or in the past 2 years, symptoms or diagnosis of a depressive disorder, bipolar spectrum disorder, OCD, PTSD, generalised anxiety disorder, severe alcohol or illegal drug dependency, psychotic disorder, anorexia nervosa, and bulimia nervosa
• Not have current symptoms or diagnosis of a panic disorder or social anxiety disorder that is not currently being treated by a psychotherapist or other mental health care professional
• Aged 18-50 years
• Fluency in English language

You may not qualify if:

• Current severe depressive (PHQ-9\>15), manic or psychotic episode, acute suicidality or suicide attempt in the past 3 months, current severe alcohol and illegal drug dependency as determined by the MINI Psychiatric Interview or clinical diagnosis.
• Pregnant, breastfeeding, or planning to be pregnant.
• Habitual fibre intake exceeding 25g/day.
• Allergy to intervention foods.
• Allergy to local anaesthesia (only if opting for the skin punch).
• Taking anticoagulant medication or have coagulation disorder like haemophilia (only if opting for the skin punch).
• Have a BMI below 18.5 kg/m2.
• Current diagnosis or symptoms of anorexia nervosa or bulimia nervosa, as determined by clinical diagnosis or on the MINI.
• Have a significant acute or chronic coexisting illness (cardiovascular, gastrointestinal, endocrinological, immunological, metabolic) or any condition which contraindicates, in the investigator's judgement, entry to the study.
• Taking antibiotics in the past month (washout period of 1 month is required).
• Taking medication that the investigator believes would interfere with the objectives of the study, pose a safety risk or confound the interpretation of the study results; to include anti-inflammatory drugs, corticosteroids, laxatives, enemas, anti-coagulants, and over-the counter non-steroidal analgesics. Participants should have a wash-out period of one month.
• Individuals who, in the opinion of the investigator, are considered to be poor attendees or unlikely for any reason to be able to comply with the trial.
• Participants receiving treatment involving experimental drugs. Washout period of one month is required.
• Current prebiotic or probiotic supplement use (a wash-out period of 4 weeks after cessation will allow entry to the study).
• Previous participation in the Diet Study (APC150)

Sponsors & Collaborators

• University College Cork: lead
• APC Microbiome Ireland, UCC: collaborator

Study Sites (1)

APC Microbiome Ireland

Cork, Cork, T12 YT20, Ireland

Location

Related Publications (6)

• Brysbaert M, Stevens M. Power Analysis and Effect Size in Mixed Effects Models: A Tutorial. J Cogn. 2018 Jan 12;1(1):9. doi: 10.5334/joc.10.

  PMID: 31517183 BACKGROUND

• Faraone SV, Biederman J, Mick E. The age-dependent decline of attention deficit hyperactivity disorder: a meta-analysis of follow-up studies. Psychol Med. 2006 Feb;36(2):159-65. doi: 10.1017/S003329170500471X.

  PMID: 16420712 BACKGROUND

• Konstanti P, Ahrens KF, Neumann RJ, Plichta MM, Schiweck C, Ruf A, Fiebach CJ, Kalisch R, Basten U, Wessa M, Tuescher O, Kollmann B, Lieb K, Arias-Vasquez A, Smidt H, Reif A, Matura S, Belzer C. Impulsivity among healthy adults is associated with diet and fecal microbiota composition. Transl Psychiatry. 2025 Aug 3;15(1):263. doi: 10.1038/s41398-025-03483-4.

  PMID: 40753077 BACKGROUND

• Berding K, Cryan JF. Microbiota-targeted interventions for mental health. Curr Opin Psychiatry. 2022 Jan 1;35(1):3-9. doi: 10.1097/YCO.0000000000000758.

  PMID: 34750307 BACKGROUND

• Ribera C, Sanchez-Orti JV, Clarke G, Marx W, Morkl S, Balanza-Martinez V. Probiotic, prebiotic, synbiotic and fermented food supplementation in psychiatric disorders: A systematic review of clinical trials. Neurosci Biobehav Rev. 2024 Mar;158:105561. doi: 10.1016/j.neubiorev.2024.105561. Epub 2024 Jan 26.

  PMID: 38280441 BACKGROUND

• Bull-Larsen S, Mohajeri MH. The Potential Influence of the Bacterial Microbiome on the Development and Progression of ADHD. Nutrients. 2019 Nov 17;11(11):2805. doi: 10.3390/nu11112805.

  PMID: 31744191 BACKGROUND

MeSH Terms

Conditions

Attention Deficit Disorder with Hyperactivity

Condition Hierarchy (Ancestors)

Attention Deficit and Disruptive Behavior Disorders; Neurodevelopmental Disorders; Mental Disorders

Central Study Contacts

Gerard Clarke, PhD

CONTACT

+3530214901224; g.clarke@ucc.ie

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: This is a double-blind study where both participants and outcomes assessors are blinded to group allocation. Randomization and assignment to dietary groups will be conducted by a staff member not involved in study visits or data analysis as well as the organisation of fermented food deliveries. Dietary counselling will be delivered by a separate dietitian who is aware of group allocation but has no role in outcome assessment or other study procedures.
• Purpose: BASIC SCIENCE
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: PhD

Study Record Dates

• First Submitted: January 21, 2026
• First Posted: January 29, 2026
• Study Start: February 1, 2026
• Primary Completion (Estimated): September 1, 2027
• Study Completion (Estimated): May 1, 2028
• Last Updated: February 12, 2026

Record last verified: 2026-02

Locations

IE (1)