Comparing the Efficacy of Accelerated vs. Standard fMRI-guided iTBS in Treating Adolescents Depression

Inclusion Criteria: 1. Voluntary and competent to consent. 2. Ages 16-19 years old. 3. Can speak and read English. 4. Primary and/or predominant diagnosis of major depressive episode without psychotic features in the current episode, confirmed by The Mini International Neuropsychiatric Interview for Children and Adolescents (MINI-KID). 5. Depressive symptoms have not improved after ≥ 1 adequate dose of antidepressant in the current depressive episode. 6. Moderate symptoms in the current depressive episode, indexed by a score of at least 40 on the Children's Depression Rating Scale Revised for depression (CDRS-R). 7. Are able to adhere to the treatment schedule. 8. Have stable psychotropic medications and/or psychotherapy regimen for at least four weeks before participating in the trial. Exclusion Criteria: 1. Diagnosis of bipolar I or II disorder, based on the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria. 2. Current or past substance (\< 3 months) (excluding caffeine or nicotine) or alcohol abuse/dependence, as defined in the DSM-5 criteria. Based on DSM-5 criteria, mild cannabis or alcohol use would be allowed in the past 3 months, moderate to severe would be an exclusion. 3. Current use of illegal substances or cannabis confirmed by urine screening test. 4. Concomitant unstable major medical or neurological disease (e.g., uncontrolled diabetes or renal dysfunction). 5. Organic cause of depressive symptoms (e.g. thyroid dysfunction), ruled out by the treating physician. 6. Acute suicidality or life-threatening due to self-neglect. 7. Are pregnant or breastfeeding, or plan to become pregnant during treatment (pregnancy will be assessed by a urine test). 8. Have a specific contraindication to TMS and/or MRI (e.g., personal history of epilepsy or seizures, metal head implant, pacemaker). 9. Unwilling to maintain the current antidepressant regimen. 10. Taking more than 1 mg/day of lorazepam or equivalent. 11. Any other condition that, in the opinion of the investigators, would impair the participant's ability to complete the study.