This is the first nationwide study using Transcranial Pulse Stimulation to evaluate its efficacy and safety on 30 young adolescents with ADHD. Six verum/ shamTPS sessions will be delivered to all subjects on a 1: 1 ratio, balanced by gender and age. Attention deficit, hyperactivity, impulsivity, and oppositional defiance will be the primary outcome. Secondary outcomes include ADHD severity, frequency of inattention, hyperactivity, impulsivity, executive function and neural connectivity changes via neuroimaging. Results emerging from this study will generate new knowledge to ascertain whether TPS can be used as a top-on treatment in ADHD.

Objectives of the study

1. To evaluate the efficacy and safety of TPS on young adolescents (12-17 years) with ADHD in Hong Kong.
2. To examine the association between TPS and ADHD core symptom severity, executive function, inattention, hyperactivity, impulsivity, and oppositional defiance.
3. To examine the brain functional connectivity changes immediately after the 2-week TPS treatment via neuroimaging.

Expected outcomes/Hypotheses:

1. Participants in the verum TPS group or the sham TPS group will have <5% somatic discomfort in the 2-week TPS intervention and that TPS is a safe intervention on young adolescents with ADHD.
2. Participants in the verum TPS group will have 30% reduction in the Swanson, Nolan, and Pelham Rating Scale (SNAP IV score) (i.e., attention deficit, hyperactivity impulse and oppositional defiance) after 2-weeks TPS treatment compared with the sham TPS group and be maintained at the 1- month & 3-month follow-up.
3. Participants in the verum TPS group will have 30% improvement in the ADHD symptoms and behaviour compared with the sham TPS group after 2-weeks TPS treatment and be maintained at the 1-month & 3-month follow-up.
4. Participants in the verum TPS group will have 30% improvement in executive function after 2 weeks TPS treatment compared with the sham TPS group and be maintained at the 1-month & 3-month follow-up.
5. Participants in the verum TPS group will have 30% improvement in both attention deficit & reduction in hyperactivity, impulsivity after 2 weeks TPS treatment compared with the sham TPS group, and be maintained at the 1 month & 3-month follow-up.
6. Participants in the verum TPS group will have more brain connectivity changes after 2-weeks TPS compared with the sham TPS group and be maintained at the 1 month & 3-month follow-up.

Design: This is a two-armed, randomized, double-blind, sham-controlled trial.

Sample size:

To the best of our knowledge, there is no interventional study evaluating the efficacy of TPS on ADHD. Based on our previous open label pilot RCT 37 evaluating TPS on adults with Major Depressive Disorder that showed a large effect size (f = 0.47), we hypothesize a large effect of TPS in this study. We used G*power version 3.1.9.4 to calculate the target sample size. With a statistical power of 95% and a statistical significance level at 0.05 to detect a large between-groups effect size (f) of 0.47 with 4 measurement time points, each group will require 15 subjects. A total sample of 30 is required in this trial. The attrition rate in our pilot MDD trial was 0%. We expect that the attrition rate in this ADHD trial would be <5%. Subject dropping out the 2-week intervention period will be replaced by another enrolled subject in this pilot study.

Intervention (Transcranial Pulse Stimulation) Purpose of the intervention: The key tenets of the TPS intervention is neuromodulation, i.e., using ultrasound-based brain stimulation techniques to modulate the human brain in a focal and targeted manner. Intervention dose: Each participant should have the pre-treatment MRI scan performed in the University Research Facility in Behavioural and Systems Neuroscience, PolyU prior coming to the first intervention session. All participants (both TPS group and the sham-control group) will receive six 30 minute-TPS sessions (800 pulse in each session, total: 4800 pulse) in 2 weeks' time. Participants will be followed up immediately after post-stimulation in Week 2, and at 1-month and 3- month period after the intervention. The investigators believe that a 2-week TPS intervention is sufficient enough to test the effects of TPS on improving inattention and hyperactivity.

Inclusion Criteria:

1. have a confirmed diagnosis of ADHD according to the 5th edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-5) of the American Psychiatric Association;
2. ethic Chinese, aged 12-17, with no co-morbidity of other mental disorders (e.g., Intellectual Disability Disorder) and organic brain diseases that affected cognitive functions;
3. no severe systemic diseases including heart, liver, lung, and kidney diseases;
4. have an IQ >80 by Stanford-Binet Intelligence Scales, 5th Edition (SB-5);
5. written consent by parents.

Exclusion Criteria:

1. SNAP IV score <1;
2. not taking ADHD medications in the past 2-4 weeks;
3. treated with TMS/rTMS/tDCS or electroconvulsive therapy in the past 12 months;
4. taking monoamine oxidase inhibitors in the past 14 days;
5. have a history of epilepsy, brain trauma, brain surgery/brain tumour, brain aneurysm or other concomitant unstable major medical conditions like haemophilia or other blood clotting disorders or thrombosis;
6. significant communicative impairments;
7. having metal implants in the brain treatment region /artificial cardiac pacemaker in-situ;
8. taking corticosteroid treatment within the last six weeks before the first TPS treatment;
9. have a history of micro-cavernomas.

Double-blind. Participants and interventionists will be blinded to the random allocation to either the verum TPS group or the sham TPS group.