L-theanine and Paraxanthine for Cognitive Improvement in Adults With ADHD and ASD

Recruiting now · Not applicable · Has a placebo group

Conditions studied: Attention Deficit Hyperactivity Disorder (ADHD), Autism Spectrum Disorder (ASD)

In brief

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.

Key facts

Study ID

NCT07189442

Run by

Texas Tech University Health Sciences Center

People needed

24

Starts

2025-10-01

Expected to finish

2026-06-01

Last updated by the study team

2026-02-05

Who can join

Age: any. Sex: male. Healthy volunteers: not accepted.

You may qualify if…

• 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

You may not qualify if…

• 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 it is running

• Texas Tech University — Lubbock, Texas, United States (enrolling)

Full record on ClinicalTrials.gov

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