Effects of L-theanine-caffeine combination on selective attention among adolescents with attention-deficit
Gayani S Nawarathna1,2, Dewasmika I Ariyasinghe3,4, Nilantha Balasooriya3,4
1Department of Physiology, Faculty of Medicine, University of Peradeniya, Peradeniya, Sri Lanka.
Background:
Attention-deficit hyperactivity disorder (ADHD) is characterized by impaired attention. L-theanine, an amino acid in tea, and caffeine, present in tea and coffee, improve attention in healthy adults.
Aim:
To investigate the acute effects of L-theanine-caffeine combination on selective attention, compared to methylphenidate and placebo, in adolescents with ADHD.
Methods:
In a double-blind, placebo-controlled, counterbalanced, three-way crossover trial, 21 adolescents with ADHD (age: 10-19 years, 18 boys) performed a computerized visual recognition reaction-time task before and 50 min after each treatment on three separate days. Participants responded to downward-pointing triangles (20% probability) while ignoring upward-pointing triangles (80%). The behavioral outcome measures were hits, false alarms, target-distractor discrimination sensitivity (A'), and hit reaction time. EEG was recorded during the task, and amplitudes and latencies of P3b event-related potentials elicited by targets in centro-parietal electrodes were measured. Pre- and post-dose changes were compared between treatments.
Results:
L-theanine-caffeine combination (P = 0.038) and methylphenidate (P = 0.035) significantly reduced false alarms versus placebo. Hits and A' showed no significant differences (P > 0.05). Only methylphenidate improved reaction time versus placebo (mean difference = 43.89 ms, P = 0.018). L-Theanine-caffeine and methylphenidate counteracted slowing of reaction time over task duration. Compared to placebo, both L-theanine-caffeine and methylphenidate increased P3b amplitudes and decreased latencies (P < 0.05).
Conclusions:
High-dose L-theanine-caffeine combination may enhance neural resource allocation and speed of deployment of selective attention, stabilize reaction speed throughout the task duration and reduce false alarms in adolescents with ADHD, supporting its potential as a nutraceutical adjunct for ADHD.Trial registration: Sri Lanka Clinical Trials Registry identifier: SLCTR/2023/004.
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