Efficacy of Convulsive Therapies During Continuation

The study will involve a parallel-group clinical trial with three treatment arms conducted at the Centre for Addiction and Mental Health (CAMH) in Toronto, ON, Ontario Shores Centre for Mental Health Sciences in Whitby, ON and University of British Columbia (UBC) Hospital in Vancouver, BC. It will include participants who are classified as responders or remitters in the CREST-MST (NCT03191058) trial, the CORRECT-BD (NCT03641300) trial and individuals responding to bitemporal ECT after participating in either of the above trials, who qualify for a continuation course of convulsive therapy to prevent relapse of depression. Individuals blinded to their acute course of treatment will continue to receive the convulsive therapy to which they responded in in a blinded fashion. Continuation treatments will be scheduled according to a modified version of the Symptom-Titrated Algorithm-based Longitudinal ECT (STABLE) algorithm. STABLE includes an initial four week period of ECT delivered on a fixed schedule (once or twice per week), and then transitions to a symptom-driven schedule whereby ECT is delivered between zero and two times per week based on the patient's weekly Hamilton Rating Scale for Depression (HRSD-24) outcomes during weeks five to 24. Further, this trial will also include non-responders to MST or right unilateral ultrabrief pulse ECT (RUL-UB ECT) from CREST-MST or CORRECT-BD, who are switched to bitemporal ECT based on their clinical indication. They will receive bitemporal ECT on an acute basis, i.e. 2 - 3 times per week. If their symptoms respond or remit with bitemporal ECT, they will also be offered a continuation course of bitemporal ECT as part of this trial and will be followed in the same manner as those receiving MST or RUL-UB ECT.