Accelerated Intermittent Theta Burst in Treatment-Naive Adolescents

Inclusion Criteria:

1. Male or Female, between the ages of 14 and 19 at the time of screening.

2. Able to read, understand, and provide written, dated assent and/or consent prior toscreening. Proficiency in English sufficient to complete questionnaires and followinstructions during aiTBS interventions. Stated willingness to comply with all studyprocedures, including availability for the duration of the study, and to communicatewith study personnel about adverse events and other clinically importantinformation.

3. Diagnosed with Major Depressive Disorder (MDD) with a current Major DepressiveEpisode (MDE), according to the criteria defined in the Diagnosis and StatisticalManual of Mental Disorders, Fifth Edition, Text Revision (DSM-5).

4. No prior major depressive episodes (MDEs) as determined by MINI-KID

5. HAMD-17 score of ≥20 at screening (Visit 1).

6. Treatment-naive as determined by the ATHF (no adequate antidepressant trials priorto screening defined as fewer than 4 weeks of antidepressant medication and fewerthan 8 psychotherapy sessions in lifetime; willingness to taper medications and stoppsychotherapy if recently started and within the window defined above.)

7. TMS naive.

8. Access to ongoing psychiatric care before and after completion of the study.

9. In good general health, as evidenced by medical history.

10. Agreement to adhere to Lifestyle Considerations throughout study duration.

Exclusion Criteria:

1. Pregnancy

2. High-risk for suicide or active suicidal ideation (Suicidal Ideation Questionnaire-Junior [SIQ-JR] ≥ 31).

3. The presence or diagnosis of prominent anxiety disorder, or dysthymia (>3 on SAPAS; >10 on GAD-7)

4. Current severe insomnia (must sleep a minimum of 5 hours each night beforestimulation)

5. Current mania or psychosis

6. Bipolar Affective Disorder and/or primary psychotic disorders.

7. Autism Spectrum disorder or Intellectual Disability

8. A diagnosis of obsessive-compulsive disorder (OCD)

9. Current moderate or severe substance use disorder or demonstrating signs of acutesubstance withdrawal.

10. Urine screening test positive for illicit substances.

11. Any history of ECT (greater than 8 sessions) without meeting responder criteria

12. Recent (during the current depressive episode) or concurrent use of a rapid actingantidepressant agent (i.e., ketamine or a course of ECT).

13. History of significant neurologic disease, including dementia, Parkinson's orHuntington's disease, brain tumor, unexpected seizure/epilepsy disorder, subduralhematoma, multiple sclerosis, or history of significant head trauma.

14. Untreated or insufficiently treated endocrine disorder.

15. Contraindications to receiving rTMS (e.g., metal in head, history of seizure, knownbrain lesion)

16. Contraindications to MRI (ferromagnetic metal in their body).

17. Any current or past history of any physical condition which in the investigator'sopinion might put the subject at risk or interfere with study resultsinterpretation.

18. Depth-adjusted aiTBS treatment dose > 65% maximum stimulator output (MSO)

19. Treatment with another investigational drug or other intervention within the studyperiod.

20. Any other condition deemed by the PI to interfere with the study or increase risk tothe participant.