This double-blind, randomized, sham-controlled clinical trial will evaluate the effects of repetitive transcranial magnetic stimulation (rTMS) on children and adolescents with attention-deficit/hyperactivity disorder (ADHD) or autism spectrum disorder (ASD) and matched healthy controls. Participants aged 6-19 years will be assigned to active or sham rTMS protocols targeting the dorsolateral prefrontal cortex over 3 weeks, with assessment of changes in disorder-specific symptoms and cortical excitability. The study aims to determine the safety, feasibility, and preliminary efficacy of rTMS as a non-invasive neuromodulation approach in pediatric neurodevelopmental disorders.

Altered cortical excitability and imbalance between excitation and inhibition have been reported in both ADHD and ASD, suggesting that non-invasive brain stimulation may modulate underlying pathophysiology. This study comprises two parallel, double-blind, sham-controlled rTMS trials in children and adolescents aged 6-19 years with ADHD or ASD and age- and sex-matched healthy controls. In the ADHD cohort, high-frequency 10 Hz rTMS will be delivered over the right dorsolateral prefrontal cortex, whereas in the ASD cohort low-frequency 1 Hz or intermittent theta-burst rTMS will be delivered over bilateral dorsolateral prefrontal cortex, each for 15 sessions over 3 weeks. Sham stimulation will mimic sound and procedure without effective magnetic pulses.

Cortical excitability will be assessed using single- and paired-pulse TMS measures (such as resting motor threshold, short-interval intracortical inhibition, long-interval intracortical inhibition, cortical silent period, and transcallosal inhibition). Blood samples will be collected to measure dopamine and brain-derived neurotrophic factor as potential neurochemical correlates. Primary clinical outcomes are changes in validated ADHD and ASD symptom rating scales, with secondary outcomes including changes in cortical excitability indices, biomarker levels, and safety/tolerability events. Data will be collected in a secure database and analyzed with mixed-effects models to estimate treatment effects and generate effect-size estimates to inform future definitive trials of rTMS in pediatric neurodevelopmental disorders.

Inclusion Criteria:

• Age 6-19 years.
• ASD trial: DSM-5 diagnosis of ASD confirmed by CARS-2.
• ADHD trial: DSM-5 diagnosis of ADHD confirmed by structured interview/CONORS
• IQ ≥ 70.
• Stable medication for ≥4 weeks (if any).

Exclusion Criteria:

• Epilepsy or seizure history.
• Metallic implants or devices incompatible with TMS.
• Severe psychiatric comorbidity (e.g., psychosis).
• Inability to tolerate TMS procedures.