Comparative Effectiveness of ECT vs. KETAMINE Over the Lifespan

Inclusion Criteria:

1. Considered by a clinician as appropriate for referral to treatment services for rapid reversal of acute suicidal depression.
2. Adults 18 - 90 years of age.
3. Meet DSM-5 criteria for Major Depressive Episode (MDE) as determined by Mini International Neuropsychiatric Interview (MINI PLUS 5.0.0).
4. Acute suicidal ideation or behavior (thinking or behavior suggesting harming or hurting oneself with knowledge that death may result) or attempt (any intentional, non-fatal self-injury regardless of medical lethality, if intent to die was indicated). \*
5. Continue to express suicidal ideation since referral as evidenced by Scale for Suicidal Ideation (SSI) ≥6)\*\*
6. Meet the following criteria on symptom rating scales at screening:

   1. Hamilton Depression Scale (HAM-D 17) \>15
   2. Montreal Cognitive Assessment (MoCA) of ≥23(to rule out baseline significant cognitive impairment)

Exclusion Criteria:

1. Meeting DSM-5 criteria for schizophrenia, schizophreniform disorder, schizoaffective disorder.
2. Not able to give informed consent to receive ECT or KET treatment.
3. Not able to give informed consent to participate in the study.
4. Meet exclusion criteria for ECT treatment as described in guidelines.
5. Meet exclusion criteria for KET treatment such as:

   1. Pregnant or breast feeding
   2. Satisfying DSM-V criteria of current Mood Depressive Disorder Episode with Psychotic Features (i.e. delusions of hallucinations)
   3. Severe uncontrolled medical illness
   4. Ketamine allergy
6. Intellectual disability and unable to provide consent or follow study procedures.