Home » Trials » SLCTR/2023/004

Acute effects of L-theanine and caffeine combination on selective attention in adolescents with attention deficit hyperactivity disorder


SLCTR Registration Number


Date of Registration

10 Mar 2023

The date of last modification

Dec 27, 2023

Application Summary

Scientific Title of Trial

Acute effects of L-theanine and caffeine combination on selective attention in adolescents with attention deficit hyperactivity disorder

Public Title of Trial

The effectiveness of L-theanine-caffeine combination given as a supplement compared to methylphenidate and placebo on improvement of selective attention in adolescents (age 10-19 years old) with attention-deficit hyperactive disorder: a double-blind, 3-way crossover trial

Disease or Health Condition(s) Studied

Attention deficit hyperactive disorder

Scientific Acronym


Public Acronym


Brief title


Universal Trial Number


Any other number(s) assigned to the trial and issuing authority


Trial Details

What is the research question being addressed?

What is the effect of L-theanine-caffeine combination on selective attention in adolescents with attention deficit hyperactive disorder compared to methylphenidate and placebo

Type of study


Study design


Non-randomized controlled trial


Double blinded : Participants, Investigators







Study Phase

Phase 4

Intervention(s) planned

1.Participants will be selected from child psychiatry outpatient clinics in Teaching Hospital Peradeniya and Sirimavo Bandaranayake Specialized Children Hospital with prior approval from relevant authorities. The study (behavioral and EEG tests) will be conducted in the Clinical Neurophysiology and Cognitive Neuroscience (CLINCON) laboratory at the Department of Physiology, Faculty of Medicine, University of Peradeniya.

2.The proposed study is a double-blind three-way crossover trial i.e., the same participant is given one treatment, and after a washout period, the other (this is the standard in crossover trials). The treatment order is counterbalanced in a Latin Square design.


Active treatment: L-theanine-caffeine combination. Dose: 2.5mg per kg body weight of L-theanine and 2.0mg per kg body weight of caffeine powder incorporated into gelatin capsules Route: Orally Single dose, post-dose test will be carried out after 45 minutes ingestion of the active treatment Frequency- once

Control: Placebo Gelatin capsule with starch equivalent to the weight of L-theanine-caffeine combination given to each participant. Route- Orally Single dose post-dose test will be carried out after 45 minutes ingestion of the placebo.

Standard therapy: methylphenidate Dose – standard dose prescribed by the psychiatrist in a Gelatin capsule Route- Orally Single dose. (This will also be the positive control, because theanine-caffeine combination is given a supplement)

The proposed study is a double-blind study where both the participant and the test administrator will be blind to the treatment given. Participant will be blinded by giving all the treatments inside a gelatin capsule and the test administrator will be blinded by giving the treatment to the participant by a third person.

Inclusion criteria

Participants must meet all of the inclusion criteria given in order to be eligible to participate in the study

  1. Patients diagnosed with attention deficit hyperactive disorder by a psychiatrist.
  2. 10-19 years old, boys and girls
  3. Patients who have responded to methylphenidate.
  4. Normal, or corrected-to-normal vision and normal hearing.

Exclusion criteria

All individuals meeting any of the exclusion criteria at baseline will be excluded from study participation

1.Gross impairment of vision or hearing that would prevent the participants from performing neuropsychological tasks 2.Inability to read and follow written instructions 3.Physical, neurological or concurrent psychiatric impairments (except ADHD) that could affect cognitive and motor functions 4.Intake of psychoactive substances which have the potential to affect cognitive functions and those which may interact with caffeine (other than their medications for ADHD) 5.Current / past diagnosis of tics or other forms of dyskinesia 6.Regular intake of medication that could alter visual, auditory, cognitive or motor functions (except stimulants) 7.History of head injury that resulted in loss of consciousness / history of brain surgery 8.Intake of drugs containing caffeine, other phosphodiesterase inhibitors or adenosine receptor blockers within the past 3 months 9.Intake of medications which are known to have pharmacological interactions with caffeine within the past 3 months 10.History of development of headache, drowsiness, anxiety, insomnia or nausea following intake of caffeine or caffeine containing beverages 11.Current / past history of smoking and / or alcohol or drug abuse 12.Unwillingness or inability to entirely refrain from use of electronic devices during study visits 13.Unwillingness or inability to refrain from intake of L-theanine and caffeine containing food or beverages within the 24 hours prior to each study visit 14.Unwillingness or inability to follow written, on-screen and verbal instructions given by the study team

Primary outcome(s)


Behavioral data Selective visual attention is the primary cognitive domain examined in the proposed experimental study. It will be evaluated by using a visual oddball paradigm developed with two sets of stimuli. Visual stimuli will be presented, and the reactions will be recorded using the Presentation® (Neurobehavioral Systems, Inc. Albany CA) software on a Windows TM-based personal computer. At the end of the test, the Presentation® software will report the following outcome measures.

  1. Hits: correct responses to targets (i.e., downward pointing triangle)
  2. False alarms: active responses made for triangles
  3. Mean hit reaction time: Time from onset of the target stimulus to response. Hits, misses, and false alarms measure the accuracy of the task and hit reaction time measures the speed.

(pre-dose) and 45 minutes after (post-dose) each treatment.


EEG data

A BioSemi Active Two EEG/ERP acquisition system with ActiView software (BioSemi, Amsterdam) will be used to acquire EEG data. A detailed description of this electrode referencing system can be found on the product website: https://www. biosemi.com/faq/cms&drl.htm. Cognitive event-related potentials (ERPs) are derived from the EEG data. ERPs waveforms are neurophysiological measures of attentive processing (P300 component) and pre-attentive processing (N1 component).

ERP data: Peak latencies and amplitudes of N1 and P300 ERP components (4 variables)


(pre-dose) and 45 minutes after (post-dose) each treatment.


Secondary outcome(s)




Target number/sample size


Countries of recruitment

Sri Lanka

Anticipated start date


Anticipated end date


Date of first enrollment


Date of study completion

Recruitment status


Funding source

University of Peradeniya Research Grant

Regulatory approvals

Not applicable

State of Ethics Review Approval



Date of Approval


Approval number


Details of Ethics Review Committee

Name: Ethics Review Committee of the Faculty of Medicine, University of Peradeniya.
Institutional Address:Ethics Review Committee, Faculty of Medicine, University of Peradeniya,
Telephone:081 -2396361

Contact & Sponsor Information

Contact person for Scientific Queries/Principal Investigator

Dr. N.G.S Nawarathna
Lecturer (probationary)
Department of Basic Sciences, Faculty of Dental Sciences, University of Peradeniya.
081 2397235


Contact Person for Public Queries

Prof. Tharaka Dassanayake
Professor in Neurophysiology
Department of Physiology, Faculty of Medicine, University of Peradeniya


Primary study sponsor/organization

Faculty of Medicine, University of Peradeniya.

34 Galaha Rd, Kandy, Sri Lanka
0812 396 000

Secondary study sponsor (If any)


Trial Completion details

Do the investigators plan to share identified individual clinical trial participant-level data (IPD)?


IPD sharing plan description

Study protocol available


Protocol version and date

Not Available

Protocol URL

Not Available

Results summary available


Date of posting results

Date of study completion

Final sample size

Date of first publication

Link to results

Brief summary of results