This trial attempts to explore the treatment outcome of magnetic seizure therapy (MST) for major depressive episode. Half of the participants will receive MST, while the other half will receive electroconvulsive therapy (ECT).

Magnetic seizure therapy (MST) is likely to be an alternative options to electroconvulsive therapy (ECT).

Widespread stimulation of cortical and subcortical regions is inevitable for ECT since the substantial impedance of the scalp and skull shuts most of the electrical stimulus away from the brain. Nevertheless, magnetic pulses are capable to focus the stimulus to a specific area of the brain because they can pass the scalp and skull without resistance. In Addition, electric current will penetrate into deeper structures, while magnetic stimulus are only capable to reach a depth of a few centimeters. As a consequence, MST are able to generate focus stimuli on superficial regions of the cortex while ECT can't, which may give MST the capability to produce comparable therapeutic benefits with the absence of apparent cognitive side effects.

Inclusion Criteria:

1. DSM-5 diagnosis of major depressive episode;
2. convulsive therapy clinically indicated, such as severe psychomotor excitement or retardation, attempts of suicide, being highly aggressive, pharmacotherapy intolerance, and ineffectiveness of antipsychotics;
3. the HAMD-17 ≥ 24;
4. informed consent in written form.

Exclusion Criteria:

1. primary diagnosis of other mental disorders;
2. severe physical diseases, such as stroke, heart failure, liver failure, neoplasm, and immune deficiency;
3. present with a laboratory abnormality that could impact on efficacy of treatments or safety of participants;
4. failure to respond to an adequate trial of ECT lifetime;
5. are pregnant or intend to get pregnant during the study;
6. Unremovable metal implants.
7. other conditions that investigators consider to be inappropriate to participate in this trial.