Comparing Uni- and Bi-lateral TBS in Major Depression

Inclusion Criteria: 1. voluntary and competent to consent to study, 2. female or male aged 18 years old or older, 3. can speak and read English and/or French 4. primary and/or predominant diagnosis of major depressive episode without psychotic features in the current depressive episode (confirmed by a Mini-International Neuropsychiatric Interview), 5. depressive symptoms have not improved after ≥ 1 adequate dose of antidepressant trial in the current depressive episode, 6. moderate symptoms in the current depressive episode as indexed by a score of at least 15 at the 17-item Hamilton Rating Scale for Depression (HRSD-17), 7. have been referred to rTMS treatment by their treating physician, and took a free and informed decision to follow this treatment, 8. are able to adhere to treatment schedule, 9. have received a stable psychiatric medication (including prescribed cannabis) or psychotherapy regimen for at least four weeks prior to entering the trial, 10. have an education-adjusted score of ≥ 24 at the Mini-Mental State Evaluation (MMSE) if are aged ≥ 65. Exclusion Criteria: 1. current or past (\< 3 months) substance (excluding caffeine or nicotine) or alcohol abuse/dependence, as defined in the Diagnostic and Statistical Manual 5th Edition (DSM-5) criteria. Based on the DSM-5 criteria, mild cannabis or alcohol use would be permissible in the past 3 months, moderate to severe would be an exclusion 2. current use of illegal substances or recreational cannabis 3. have a concomitant major unstable medical or neurologic illness (e.g. uncontrolled diabetes or renal dysfunction), 4. organic cause to the depressive symptoms (e.g. thyroid dysfunctions), determined by the referring physician 5. acute suicidality or threat to life from self-neglect, 6. are pregnant or breastfeeding, or thinking of becoming pregnant during course of treatment, 7. have a specific contraindication for TMS (e.g., personal history of epilepsy or seizure, metallic head implant, pacemaker), 8. unwilling to maintain current antidepressant regimen, 9. are taking more than 1 mg of lorazepam or equivalent, 10. any other condition that, in the opinion of the investigators, would adversely affect the participant's ability to complete the study, 11. have failed a course of electroconvulsive therapy (ECT) within the current depressive episode due to the lower likelihood of response to rTMS.If they have had failed ECT in the past, this does not exclude them