Esketamine vs ECT for Acute Suicidality

Inclusion Criteria (all five criteria must be met for an individual to be included): 1. Outpatients or inpatients aged 18 to 65 years (inclusive); 2. Having a current diagnosis of MDD or depressive episode in bipolar I/II disorder, established using the Mini-International Neuropsychiatric Interview, version 7.0.2 (MINI 7.0.2) and according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria; 3. Having a total score of 6 or more on the SSI at screening; 4. Having at least primary school education and the ability to comprehend assessment scales; 5. Having provided written informed consent. Exclusion Criteria (an individual will be excluded if any one of the following criteria is met): 1. Having a current or historical diagnosis of neurodevelopmental, neurocognitive, psychotic, or substance-related disorders according to the DSM-5 criteria; 2. Having active delusions or hallucinations; 3. Suffering from severe/unstable systemic illness (illness affecting the central nervous system, cardiovascular, respiratory, hepatic, renal, endocrine, or hematologic systems) and judged by the investigator as unsuitable for participation; 4. Being judged by the investigator as at risk for substance abuse or addiction; 5. Using reserpine currently; 6. Contraindications to general anesthesia; 7. Having a history of seizure disorders (except for uncomplicated childhood febrile seizures); 8. Having severe drug or food allergies or allergy to any component of the study medication; 9. Having a history of treatment non-response or severe adverse reactions to esketamine, ketamine, or ECT; 10. Having participated in any other clinical trials within the three months before the enrollment; 11. Being pregnant, breastfeeding, or planning to become pregnant (for female participants) or planning to father a child (for male participants) during the study or within 12 weeks after the last dose of medication; 12. Being judged by researchers as unsuitable for participation.