NCT07189442 · Texas Tech University Health Sciences Center
L-theanine and Paraxanthine for Cognitive Improvement in Adults With ADHD and ASD
What this study is about
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 randomly assigned, single-blinded, repeated-measures crossover trials will be conducted.
View original scientific description
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.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- 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
Exclusion criteria
- 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
- 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.
Where
- Lubbock, Texas
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Feb 5, 2026 · Source of record for eligibility and locations