BackgroundElectroconvulsive therapy (ECT) is the most rapid and effective treatment for patients with depression, ECT can achieve remarkable antidepressant effects in the initial 3-4 sessions, but significant side effects limit its use. However, recent low-charge electrotherapy (LCE) studies have demonstrated antidepressant or antipsychotic effects with significantly fewer side effects. The aim of this study is to propose a novel two-step charge set strategy for ECT treatment, referred to as Hybrid-ECT, to decrease side effects by using a low charge while preserving treatment efficacy.Methods/designA randomized, double-blinded, standard-controlled, parallel-group design will be carried out. We plan to enroll 112 inpatients diagnosed with depression (unipolar or bipolar) and randomly assign them to conventional ECT (control group) or to Hybrid-ECT (treatment group, 3 ECT sessions followed by LCE sessions (approximately 2.8 joules per session)). We will evaluate participants across a wide variety of domains including clinical symptoms, cognitive, psychological and functional metrics. We will also perform magnetic resonance imaging (MRI) and event-related potential (ERPs) assessments during treatment to explore brain function differences between ECT and LCE.DiscussionThis research proposes a simple but completely novel ECT strategy that aims to rapidly relieve depressive symptoms and minimize side effects. The mechanism of ECT and LCE will be further discussed.Trial registrationChinese Clinical Trial Registry, Number: ChiCTR1900022905 (Registration date: April 30, 2019).