Eligibility Details:  
        -  INCLUSION CRITERIA:
        Phase I: Groups 1-3 and 5 (Patients)
          1. 18 to 70 years of age.
          2. A level of understanding sufficient to agree to all required tests and examinations,
             sign an informed consent document and verify understanding by a score greater than or
             equal to 90% on the Baseline consent quiz
          3. Individuals who are able to get pregnant must be willing to remain sexually abstinent
             or use at least one form of effective birth control during participation in Phase I.
          4. Additional Criteria for Group 1 (Active Crisis): Agree to be hospitalize
        Phase I: Group 4 (Healthy Volunteers)
          1. 18 to 70 years of age.
          2. A level of understanding sufficient to agree to all required tests and examinations,
             sign an informed consent document.
          3. Individuals who are able to get pregnant must be willing to remain sexually abstinent
             or use at least one form of effective birth control during participation in Phase I.
        Phase II: Group 1 (Active Crisis)
          1. Patients must have completed Study Phase I as a participant in Group 1
          2. Participants must verify understanding of the protocol by a score greater than or
             equal to 80% on the Ketamine Response
             consent quiz.
          3. Patients must report at least minimal suicidal ideation, depressive or anxiety
             symptoms to be eligible for this phase (see Monitoring Suicide Risk section).
               -  MADRS score of over 10 (10 used as an outcome measure for remission)126
               -  OR HAMA score of over 7 (7 used as an outcome measure for remission)127
               -  OR SSI score of 2 or more (indicates any residual suicidal thoughts)
          4. Individuals who are able to get pregnant must be willing to remain sexually abstinent
             or use at least one form of effective birth control during participation in Phase II.
        Phase III: Group 1 (Active Crisis)
          1. Participants must have met all inclusion criteria for and completed Study Phase II as
             a participant in Group 1 (active crisis)
          2. Individuals who are able to get pregnant must be willing to remain sexually abstinent
             or use at least one form of effective birth control during participation in Phase III.
        EXCLUSION CRITERIA:
        Phase I: Groups 1-3 and 5 (Patients)
          1. Current psychotic features or cognitive impairment that would preclude understanding
             of the consenting process or tests/examinations.
          2. Current drug or alcohol dependence
          3. Currently intoxicated or under the acute effects of an illicit substance will not be
             consented into the study.
          4. Pregnant or nursing individuals or those who plan to become pregnant.
          5. Serious, unstable medical conditions/problems including hepatic, renal,
             gastroenterologic, respiratory, cardiovascular (including blood pressure, ischemic
             heart disease), endocrinologic, neurologic, immunologic, or hematologic disease.
          6. Clinically significant abnormal laboratory tests.
          7. Positive HIV test
          8. Participants who, in the investigator s judgment, pose a current homicidal risk or
             pose suicide risk that cannot be managed in a secure, voluntary inpatient setting.
          9. Non-English speakers
         10. Additional Criteria for Group 1 (Active Crisis): For participants who still experience
             the effects of their suicide attempt, i.e. someone who overdosed is significantly
             drowsy or confused, the consenting process will occur after the patient has improved
             from the effects. If there is a concern around a participant s capacity to consent,
             the Human Subjects Protections Unit (HSPU) team member who is
        monitoring the informed consent process will complete a capacity assessment. Participants
        who are determined not to have capacity to consent to research will not be included in the
        study.
        Phase I: Group 4 (Healthy Volunteers)
          1. Current or past Axis I diagnosis
          2. Presence of medical illness likely to alter brain morphology and/or physiology (e.g.,
             hypertension, diabetes) even if controlled by medications.
          3. Current or past alcohol or substance abuse or dependence diagnosis (except for
             nicotine or caffeine) (or substance abuse disorder per DSM-V).
          4. Presence of psychiatric disorders or a history of suicide attempt or death in
             first-degree relatives.
          5. Pregnant or nursing individuals or those who plan to become pregnant.
          6. No lifetime suicide attempts or ideations
          7. Non-English speakers
          8. Positive HIV test
        Exclusions for Imaging:
          1. Participants with metal objects implanted in the body, such as aneurysm clips, neural
             stimulators, implanted cardiac pacemakers, or auto-defibrillator, cochlear implant, or
             ocular foreign body which would make having an MRI scan unsafe
          2. Participants who are uncomfortable in small closed spaces (have claustrophobia) and
             would feel uncomfortable in the MRI machine
          3. Participants with a brain abnormality on an initial MRI scan
          4. Subjects with hearing loss that has been clinically evaluated and diagnosed and may be
             worsened through participation in imaging procedures
        Phase II: Group 1 (Active Crisis)
          1. Treatment with a reversible MAOI within 2 weeks prior to study Phase II.
          2. Treatment with any other concomitant medication not allowed within 5 (Omega)
             half-lives prior to study Phase II.
          3. Subjects with one or more seizures without a clear and resolved etiology
          4. Participants with a positive urine for an illicit substance no more than 24 hours
             prior to the ketamine infusion.
          5. Presence of current psychotic features or a diagnosis of Schizophrenia or any other
             psychotic disorder as defined in the DSM-IV or DSM-V
          6. Pregnant or nursing individuals or those who plan to become pregnant.
          7. A medical finding or condition that in the clinical judgement of the investigator
             increases the risk of adverse effects from the ketamine administration (for example:
             findings suggesting difficulties with kidney or cardiac function that may be
             contraindications for an experimental intervention).
        Phase III: Repeated Administration (Group 1 only)
          1. Intolerable or serious adverse reaction to ketamine during Phase II
          2. Treatment with a reversible MAOI within 2 weeks prior to study Phase III.
          3. Treatment with any other concomitant medication not allowed within 5 (Omega)
             half-lives prior to study Phase III.
          4. Subjects with one or more seizures without a clear and resolved etiology
          5. Participants with a positive urine for an illicit substance no more than 24 hours
             prior to each ketamine infusion.
          6. Presence of current psychotic features or a diagnosis of Schizophrenia or any other
             psychotic disorder as defined in the DSM-IV or DSM-V
          7. Pregnant or nursing individuals or those who plan to become pregnant.
        Exclusions for Imaging:
          1. Participants with metal objects implanted in the body, such as aneurysm clips, neural
             stimulators, implanted cardiac pacemakers, or auto-defibrillator, cochlear implant, or
             ocular foreign body which would make having an MRI scan unsafe
          2. Participants who are uncomfortable in small closed spaces (have claustrophobia) and
             would feel uncomfortable in the MRI machine
          3. Participants with a brain abnormality on an initial MRI scan
          4. Subjects with hearing loss that has been clinically evaluated and diagnosed and may be
             worsened through participation in imaging procedures