Medications will be continued during rTMS if considered safe to do so. Patients will only enter the study if there has been no dose increase in the 4 weeks prior to randomization and there has been no significant improvement (>15% change) in depression in one week between screening and the first study assessment visit (based on HAMD ratings at these two visits). The commencement of any new psychotropic medication will not be allowed in the 4 weeks prior to study entry and during the study period. The continuation of antidepressant medication / mood stabilizers places the trial in a realistic clinical framework. We will minimize the confounding effect of medication by: