The Impact of AMPA Receptor Blockade on Ketamine's Anti-Suicidal Effects

Inclusion Criteria: * Current depression as indicated by a score greater than 17 on the full Hamilton Depression Rating Scale (HDRS-17) AND current major depressive episode as determined by structured clinical interview (SCID-5) * Current suicidal ideation as indicated by a score ≥ 2 on the HDRS-17 Item #3 ("wishes to be dead (or any thoughts of possible death to self)") * Anti-depressant resistant depressive symptoms, defined by a history of failure of one or more adequate anti-depressant trials * Participants will meet DSM-5 Criteria for MDD, PTSD or Bipolar Disorder as determined by the SCID-5 * All participants given Ketamine must be engaged in mental health treatment outside of the research protocol. Those who are not receiving treatment with a mental health provider at the time of the phone screen may be referred for treatment and will have their admission to the protocol deferred until they are receiving treatment with a mental health provider for at least 4 weeks, at which time they may re-apply for admission to the protocol. * Individuals who are receiving pharmacotherapy for depression must have been receiving the current medication and dose for 4 weeks before randomization. Those who are not stable on their current medication and dose for 4 weeks at the time of the phone screen may have their admission to the protocol deferred until they are stable on their current psychopharmacotherapy. In addition, all individuals admitted to the protocol should have a plan to c…