Attention Deficit Hyperactivity Disorder (ADHD)NCT07189442
L-theanine and Paraxanthine for Cognitive Improvement in Adults With ADHD and ASD
A study testing L-theanine and paraxanthine in people with Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD), run by Texas Tech University Health Sciences Center at 1 site in United States.
Trial summary
This pilot study will test whether combining L-theanine and paraxanthine improves sustained attention, inhibitory control, and overall cognition in adults with ADHD and ASD. Two parallel randomized, single-blinded, repeated-measures crossover trials will be conducted. Read more about this study
- Who is it for?
- Any age, men only
- Conditions the study is for
- Attention Deficit Hyperactivity Disorder (ADHD), Autism Spectrum Disorder (ASD)
- What is being tested?
- L-theanine and paraxanthine
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 17 participants
- Where
- 1 siteUnited States
- Study dates
- 1 Oct 2025to 1 Jun 2026
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages Any age
- Men only
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- Adults (18+ years) diagnosed by a physician (per self-report) with ADHD or ASD
- Participants with a dual diagnosis and ASD and ADHD will be recruited but will only be included in the ASD group - their concurrent ADHD diagnosis will be included as an additional variable in exploratory analyses
Who cannot join
- Subjects with gross visual or auditory impairments that might limit their ability to perform neuropsychological tasks
- Inability to read and follow written instructions
- Physical, neurological, intellectual, or psychiatric impairments (except ADHD or ASD) that could affect cognitive and motor functions
- Subjects on medications including antidepressants and antipsychotics that may affect performance in the tasks
- Subjects on medications that are likely to interact with the administered substances, including regular intake of medication that could alter visual, auditory, cognitive, or motor functions (except stimulants)
- History of head injury resulting in loss of consciousness/history of brain surgery
Show all 16Show fewer
- Subjects who have developed adverse effects when caffeine/paraxanthine /L-theanine/corn starch (will be in placebo) containing products were consumed
- Subjects who are unwilling or unable to refrain from intake of L-theanine/ caffeine/ paraxanthine containing food or beverages within the 24 hours prior to each study visit
- Intake of drugs containing caffeine, other phosphodiesterase inhibitors, or adenosine receptor blockers within the past 3 months
- Intake of medications known to have pharmacological interactions with paraxanthine within the past 3 months
- Current/past diagnosis of tics or other forms of dyskinesia
- History of headache, drowsiness, anxiety, insomnia, or nausea following intake of caffeine or caffeine-containing beverages
- Current/past history of smoking and/or alcohol or drug abuse
- Subjects with absolute contraindications to undergo MRI after being screened by the TTNI safety screening sheet (Appendix)
- Unwillingness or inability to entirely refrain from the use of electronic devices during study visits
- Unwillingness or inability to follow written, on-screen, and verbal instructions given by the study team.
Trial locations and contacts
1 site in 1 country.
About this study
Official title: Combining L-theanine and Paraxanthine for Transient Improvement of Cognitive Deficits Among Patients With Attention Deficit Hyperactivity Disorder and Autism Spectrum Disorder: A Series of Translational Pilot Neuroimaging Studies
This pilot study will test whether combining L-theanine and paraxanthine improves sustained attention, inhibitory control, and overall cognition in adults with ADHD and ASD. Two parallel randomized, single-blinded, repeated-measures crossover trials will be conducted. Participants will complete neuropsychological testing, fMRI scanning, and self-report measures following administration of the L-theanine-paraxanthine combination compared to placebo.
Read the detailed description
Improving cognitive functions, including how fast the brain processes information, staying focused, and controlling impulsive actions, has been a topic of interest for centuries. These functions are frequently impaired in developmental or neurological conditions like attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Although medications like amphetamines can help manage cognitive deficits, they often carry significant side effects, risk of addiction, and high costs. Consequently, many individuals and families turn to complementary and alternative treatments. For instance, people with neurodevelopmental conditions, including ADHD, may consume more caffeinated beverages in the hope of boosting cognitive performance. This highlights the need for the exploration of commonly available alternative approaches to determine their efficacy. This study specifically aims to investigate an alternative approach that could serve as a more affordable, integrative, and complementary treatment modality for ADHD and ASD.
Findings of recent controlled cognitive and fMRI studies corroborate the findings of others to indicate that intake of two constituents of tea and coffee, namely L-theanine and caffeine, improves sustained attention in healthy young adult males by decreasing mind wandering. Interestingly, when administered together, L-theanine and caffeine synergistically acted to reduce mind wandering while engaged in a cognitively demanding task. Given the low cost and safety, oral administration of the L-theanine-caffeine combination seems to be a promising strategy to alleviate ADHD-associated impairments of sustained attention. However, regular high consumption of caffeine has adverse effects, such as jitteriness and sleep disturbance due to its metabolites, and the metabolism of caffeine has individual variability.
Paraxanthine is an active metabolite of caffeine that has cognitive benefits without adverse effects and predictable metabolism. However, the effects of the L-theanine-paraxanthine combination on improving cognitive deficits of adults with ADHD and ASD have not been examined. It is expected that combining theanine with paraxanthine instead of caffeine would result in more predictable, consistent, and possibly more marked improvements. There is a critical need to establish the efficacy and mechanisms of action of the L-theanine-paraxanthine combination in order to improve ADHD and ASD-related cognitive deficits. Therefore, the investigators plan to conduct a randomized, single-blinded, repeated-measures crossover trial to answer the following research questions.
- Being tested
- L-theanine and paraxanthine, Placebo
- Keywords
- ADHD, Attention Deficit Hyperactivity Disorder, ASD, Autism spectrum disorder, Autism
- Medical subject headings
- Attention Deficit Disorder with Hyperactivity, Autism Spectrum Disorder, Autistic Disorder
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
L-theanine and paraxanthineDietary supplement
200 mg L-theanine + 200 mg paraxanthine capsule
PlaceboDietary supplement
400 mg corn starch capsule
| Study group | Role | What they receive |
|---|---|---|
| Attention deficit hyperactivity disorder (ADHD) | Experimental | A group of 12 adult males with Attention Deficit Hyperactivity Disorder (ADHD) will be enrolled. Each participant will receive both study conditions in a randomized, single-blinded, repeated-measures crossover design:
Active Condition: One capsule containing 200 mg L-theanine + 200 mg paraxanthine.
Placebo Condition: One capsule containing 400 mg of corn starch. The order of administration will be randomized, with each participant completing both conditions on separate visits (visits 2 and 3). Receives: Dietary Supplement: L-theanine and paraxanthine; Dietary Supplement: Placebo |
| Autism spectrum disorder (ASD) | Experimental | A group of 12 adult males with autism spectrum disorder (ASD) will be enrolled. Each participant will receive both study conditions in a randomized, single-blinded, repeated-measures crossover design:
Active Condition: One capsule containing 200 mg L-theanine + 200 mg paraxanthine.
Placebo Condition: One capsule containing 400 mg of corn starch. The order of administration will be randomized, with each participant completing both conditions on separate visits (visits 2 and 3). Receives: Dietary Supplement: L-theanine and paraxanthine; Dietary Supplement: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
fMRI task-related activity
fMRI task-related activity in default mode and central executive networks during Go/NoGo and Stop-Signal tasks.
Measured: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo.
Stop Signal Reaction Time
Estimated time (milliseconds) required to inhibit a prepotent response following a stop signal, computed using the horse-race model and drift-diffusion theory. Lower values indicate better inhibitory control.
Measured: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo. This task is performed while in the MRI.
d-prime (sensitivity to the Go signal)
d-prime on Go/No-Go task computed using the signal detection theory.
Measured: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo. This task is performed while in the MRI.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted24 Sep 2025
- Study start1 Oct 2025
- Primary completion1 Jun 2026
- Study completion1 Jun 2026
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Attention Deficit Hyperactivity Disorder (ADHD)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Model description
- Crossover Assignment (two-way, repeated measures)
- Masking
- Single blind
- Who is masked
- Participant
- Enrolment
- 17 participants (actual)
Sponsor and investigators
- Lead sponsor
- Texas Tech University Health Sciences Center
- Sponsor type
- University, hospital or other
- Collaborators
- Texas Tech University
- Responsible party
- Principal investigator, Samudani Dhanasekara, Texas Tech University Health Sciences Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07189442
- Sponsor's protocol ID
- IRB2025-147
- Status last verified
- Feb 2026
- First submitted
- 16 Sep 2025
- Last updated
- 24 Aug 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No: De-identified individual participant data may be shared with qualified researchers upon a reasonable request and after obtaining institutional approval.
Study at a glance
From the registry record, last updated by the sponsor on 24 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Combining L-theanine and Paraxanthine for Transient Improvement of Cognitive Deficits Among Patients With Attention Deficit Hyperactivity Disorder and Autism Spectrum Disorder: A Series of Translational Pilot Neuroimaging Studies
- ClinicalTrials.gov ID
- NCT07189442
- Acronym / sponsor ID
- IRB2025-147
- Keywords
- ADHD, Attention Deficit Hyperactivity Disorder, ASD, Autism spectrum disorder, Autism
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 17 participants (actual)
- Lead sponsor
- Texas Tech University Health Sciences CenterUniversity, hospital or other
- Collaborators
- Texas Tech University
- Study start
- 1 Oct 2025 (actual)
- Primary completion
- 1 Jun 2026 (actual)
- Study completion
- 1 Jun 2026 (actual)
- First posted
- 24 Sep 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This pilot study will test whether combining L-theanine and paraxanthine improves sustained attention, inhibitory control, and overall cognition in adults with ADHD and ASD. Two parallel randomized, single-blinded, repeated-measures crossover trials will be conducted. Participants will complete neuropsychological testing, fMRI scanning, and self-report measures following administration of the L-theanine-paraxanthine combination compared to placebo.
Detailed description
Improving cognitive functions, including how fast the brain processes information, staying focused, and controlling impulsive actions, has been a topic of interest for centuries. These functions are frequently impaired in developmental or neurological conditions like attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). Although medications like amphetamines can help manage cognitive deficits, they often carry significant side effects, risk of addiction, and high costs. Consequently, many individuals and families turn to complementary and alternative treatments. For instance, people with neurodevelopmental conditions, including ADHD, may consume more caffeinated beverages in the hope of boosting cognitive performance. This highlights the need for the exploration of commonly available alternative approaches to determine their efficacy. This study specifically aims to investigate an alternative approach that could serve as a more affordable, integrative, and complementary treatment modality for ADHD and ASD.
Findings of recent controlled cognitive and fMRI studies corroborate the findings of others to indicate that intake of two constituents of tea and coffee, namely L-theanine and caffeine, improves sustained attention in healthy young adult males by decreasing mind wandering. Interestingly, when administered together, L-theanine and caffeine synergistically acted to reduce mind wandering while engaged in a cognitively demanding task. Given the low cost and safety, oral administration of the L-theanine-caffeine combination seems to be a promising strategy to alleviate ADHD-associated impairments of sustained attention. However, regular high consumption of caffeine has adverse effects, such as jitteriness and sleep disturbance due to its metabolites, and the metabolism of caffeine has individual variability.
Paraxanthine is an active metabolite of caffeine that has cognitive benefits without adverse effects and predictable metabolism. However, the effects of the L-theanine-paraxanthine combination on improving cognitive deficits of adults with ADHD and ASD have not been examined. It is expected that combining theanine with paraxanthine instead of caffeine would result in more predictable, consistent, and possibly more marked improvements. There is a critical need to establish the efficacy and mechanisms of action of the L-theanine-paraxanthine combination in order to improve ADHD and ASD-related cognitive deficits. Therefore, the investigators plan to conduct a randomized, single-blinded, repeated-measures crossover trial to answer the following research questions.
Study design
- Primary purpose
- Other
- Allocation
- Randomised
- Intervention model
- Crossover
- Masking
- Single blind (participant)
- Number of arms
- 2
- Model description
- Crossover Assignment (two-way, repeated measures)
| Arm | Type | Receives |
|---|---|---|
| Attention deficit hyperactivity disorder (ADHD) | Experimental | Dietary Supplement: L-theanine and paraxanthine, Dietary Supplement: PlaceboA group of 12 adult males with Attention Deficit Hyperactivity Disorder (ADHD) will be enrolled. Each participant will receive both study conditions in a randomized, single-blinded, repeated-measures crossover design: Active Condition: One capsule containing 200 mg L-theanine + 200 mg paraxanthine. Placebo Condition: One capsule containing 400 mg of corn starch. The order of administration will be randomized, with each participant completing both conditions on separate visits (visits 2 and 3). |
| Autism spectrum disorder (ASD) | Experimental | Dietary Supplement: L-theanine and paraxanthine, Dietary Supplement: PlaceboA group of 12 adult males with autism spectrum disorder (ASD) will be enrolled. Each participant will receive both study conditions in a randomized, single-blinded, repeated-measures crossover design: Active Condition: One capsule containing 200 mg L-theanine + 200 mg paraxanthine. Placebo Condition: One capsule containing 400 mg of corn starch. The order of administration will be randomized, with each participant completing both conditions on separate visits (visits 2 and 3). |
Who may qualify
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (2 listed)
- Adults (18+ years) diagnosed by a physician (per self-report) with ADHD or ASD
- Participants with a dual diagnosis and ASD and ADHD will be recruited but will only be included in the ASD group - their concurrent ADHD diagnosis will be included as an additional variable in exploratory analyses
Key exclusion criteria (16 listed)
- Subjects with gross visual or auditory impairments that might limit their ability to perform neuropsychological tasks
- Inability to read and follow written instructions
- Physical, neurological, intellectual, or psychiatric impairments (except ADHD or ASD) that could affect cognitive and motor functions
- Subjects on medications including antidepressants and antipsychotics that may affect performance in the tasks
- Subjects on medications that are likely to interact with the administered substances, including regular intake of medication that could alter visual, auditory, cognitive, or motor functions (except stimulants)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| L-theanine and paraxanthine200 mg L-theanine + 200 mg paraxanthine capsule | Dietary supplement | Attention deficit hyperactivity disorder (ADHD), Autism spectrum disorder (ASD) |
| Placebo400 mg corn starch capsule | Dietary supplement | Attention deficit hyperactivity disorder (ADHD), Autism spectrum disorder (ASD) |
Primary outcome
fMRI task-related activity
Time frame: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo.
fMRI task-related activity in default mode and central executive networks during Go/NoGo and Stop-Signal tasks.
Stop Signal Reaction Time
Time frame: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo. This task is performed while in the MRI.
Estimated time (milliseconds) required to inhibit a prepotent response following a stop signal, computed using the horse-race model and drift-diffusion theory. Lower values indicate better inhibitory control.
d-prime (sensitivity to the Go signal)
Time frame: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo. This task is performed while in the MRI.
d-prime on Go/No-Go task computed using the signal detection theory.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Aug 2026.
- Individual participant dataSharing planned: No. De-identified individual participant data may be shared with qualified researchers upon a reasonable request and after obtaining institutional approval.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing L-theanine and paraxanthine in people with Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD), run by Texas Tech University Health Sciences Center at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 16 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 24 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
fMRI task-related activity (time frame: At visit 2 or 3, 30 minutes after intake of L-theanine-paraxanthine or placebo.). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Aug 2026.