Repetitive transcranial magnetic stimulation (rTMS) is a Health Canada approved treatment for major depression. Theta burst stimulation (TBS), a type of rTMS, is a very promising new treatment for major depression in adults and adolescents. However, very few studies have assessed the efficacy of accelerated, three times a day TBS in comparison with standard once a day TBS in adolescents. The study aims to explore further evidence in hopes to conduct a large-scale, randomized, multisite, placebo-controlled clinical trial evaluating the effects of a functional magnetic resonance imaging (fMRI)-guided accelerated rTMS protocol vs. standard once/daily rTMS for treatment-resistant depression in adolescents.

Recently the efficacy of repetitive Transcranial Magnetic Stimulation (rTMS) has significantly improved for Treatment-Resistant Depression (TRD) in adults and promising evidence suggesting safety and efficacy of rTMS in adolescents. These youth studies currently use outdated stimulation protocols, with most of them using treatments on a once/daily schedule. Given the prevalence, morbidity, and mortality associated with depression in adolescents, and considering that over 40% of adolescents do not respond to medications, a randomized controlled trial (RCT) to establish the safety and efficacy of new rTMS protocols for difficult-to-treat depression in adolescents is desperately needed.

This open-label randomized controlled trial will compare accelerated intermittent theta burst stimulation (iTBS) and standard once a day iTBS in adolescents with major depressive disorder (MDD). For this pilot trial, 10 adolescents (5 females, 5 males) with treatment-resistant depression will be recruited. Each participant will undergo a 30-40-minute magnetic resonance imaging (MRI) scan, after which they will receive iTBS applied to the left dorsolateral prefrontal cortex (DLPFC) once a day for 6 weeks (standard treatment) or for an accelerated duration of 3 times a day for 2 weeks. Symptoms will be assessed through clinical assessments as well as self-report questionnaires. Prior to treatment start each participant will complete the clinical assessments as well as the self-report questionnaires for a baseline measurement. The self-report measures will be completed every 5th treatment (total of 7 times including baseline). The clinical assessments will be completed after the 15th and 30th treatment, as well as 2-,4-, and 12-weeks post treatment course (total of 6 times including baseline). The main outcome of this trial is a clinical response rate which will be defined as a ≥ 50% reduction in depressive symptoms based off of the Children's Depression Rating Scale Revised for depression (CDRS-R). The secondary outcome of this trial is suicidal ideation which will be measured by the Beck Scale for Suicidal Ideation (BSS), as well as several other outcomes such as anxiety, sleep quality, physical activity and stress. The ultimate goal of this study is to provide initial evidence for conducting a large-scale, randomized, multisite, placebo-controlled clinical trial evaluating the effects of an fMRI-guided accelerated rTMS protocol vs. standard once/daily rTMS for treatment-resistant depression in adolescents.

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.

All Individual Participant Data collected from this study (IPD) will be de-identified for all parties who have permission to access it. This de-identified data may be shared with other researchers at the Royal's Institute of Mental Health Research. De-identified may be shared with the public only upon request. Please note that all data that has the potential of revealing participants' identity will NOT be used to shared.

De-identified data may become available (upon request) when the study is completed and published (anticipated time frame: the year of 2026)

De-identified data will be accessible only through the permission of the lead research scientist. All requests must be made and accepted by her.