Comparing Uni- and Bi-lateral TBS in Major Depression

This study is comparing one-sided versus two-sided brain stimulation using a technique called TBS (theta burst stimulation — a rapid type of rTMS/magnetic brain stimulation) for people with major depression who have not responded to antidepressant medication. **You may be eligible if...** - You are 18 or older and can speak and read English or French - You have been diagnosed with a major depressive episode without psychotic features - You have not improved after at least one adequate course of antidepressant medication in your current depressive episode - Your depression symptoms are moderate to severe (Hamilton Rating Scale score of at least 15) - Your doctor has referred you for rTMS treatment - Your psychiatric medication (if any) has been stable for at least 4 weeks **You may NOT be eligible if...** - You have epilepsy, a metal implant in the head, or a pacemaker (contraindications to TMS) - You have a serious unstable medical or neurological illness - You are pregnant or breastfeeding, or planning to become pregnant during the trial - You have recently failed electroconvulsive therapy (ECT) in the current episode - You are acutely suicidal - You are currently using illegal substances or more than 1 mg of lorazepam (or equivalent) daily Talk to your doctor to see if this trial is right for you.