Business decision to stop enrollment after 1 participant completed the study. Will not be reopening.

This observational study will allow data to be collected to demonstrate changes in brain activity following administration of standard of care (SOC) Ketamine. By comparing genetic markers across participants, data on impact of genetic markers and response to Ketamine will also be analysed. This data will contribute to the design of future studies utilizing Ketamine for various psychiatric disorders. This study will focus on treatment-resistant Major Depressive Disorder (MDD).

This is an Open Label Observational Study with the primary objective to assess brain activity in patients prior to, during and after Ketamine treatment and to assess genetic markers prior to Ketamine treatment. This is a non-interventional study that will observe the Electroencephalogram (EEG) pattern of participants who, per standard of care, are treated with intramuscular Ketamine. The administration of the Ketamine during this study is not considered investigational. The experimental intervention, measurements via EEG, will be offered to patients of the study site presenting for intramuscular (IM) ketamine treatment per the site's established and evidence-based protocol as part of their regular clinical care. Participants in this study have already been determined to have a medically appropriate indication for IM Ketamine treatment, independent of enrollment in this study. Given the requirement, per study protocol, to wear an EEG headset and complete study measures, participants will be compensated by having treatment costs paid by the study sponsor. There will be 36 participants enrolled at one study site.

Inclusion Criteria:

1. Primary Diagnostic and Statistical Manuel of Mental Disorders 5 (DSM-V) diagnosis of treatment-resistant Major Depressive Disorder (may have secondary diagnoses of general anxiety, substance disorder)

   • Non-responders to at least 2 previous anti-depressant medications prescribed by a physician in the past five years
   • Score of ≥20 on Montgomery-Asberg Depression Rating Scale (MADRS) (i.e., moderate to severe depression)

2. All genders aged 21 to 60 years of age

3. Prescribed Ketamine or currently being treated with Ketamine for treatment-resistant Major Depressive Disorder

4. Willing to wear an Electroencephalogram (EEG) headset and an eye mask

5. Willing to listen to ambient sound

6. Willing to have a genetic cheek swab

Exclusion Criteria:

1. Pregnancy

2. Traumatic Brain Injury within past 3 months

3. Body weight < 50 kg or > 120 kg

4. Coronary heart disease

5. Uncontrolled hypertension as defined in the American College of Cardiology/American Heart Association (ACC/AHA) Hypertension Guidelines

6. Previous contact with Ketamine (therapeutically or recreationally) outside of treatment at the study site

7. Primary psychotic disorder (e.g., schizophrenia, schizoaffective disorder)

8. Bipolar disorder with current manic, hypomanic or mixed state

9. Post-traumatic stress disorder

10. Obsessive-compulsive disorder

11. Primary substance-use disorder

12. Alcohol consumption 24 hours prior and 48 hours subsequent to treatment

13. Currently using any of the following medications:

    • Benzodiazepines for 6 hours prior to treatment and 2 hours after treatment
    • Lamotrigine for 6 hours prior to treatment
    • Amphetamine-based stimulants for 6 hours prior to treatment
    • Monoamine Oxidase Inhibitors (MAO-Is) may be taken but blood pressure must be monitored

Male or female participants with treatment-resistant Major Depressive Disorder aged 21-60 interested in receiving intra-muscular injections of ketamine over 10 sessions in the clinic and willing to wear an electroencephalogram (EEG) headset to measure their brain wave patterns.