This is a feasibility study, to investigate a new treatment option for major depressive disorders by performing a Stellate Ganglion Block (SGB). A SGB is an injection of local anesthetic into the sympathetic nervous system (peripheral nervous system) located in the lower part of the neck, to relieve pain in the head, neck, upper arm, and upper chest.

Inclusion Criteria:

1. 18 - 65 years of age
2. Major depressive disorder without psychotic symptoms according to DSM-5 criteria
3. Hamilton Depression Rating Scale (HAMD)>17
4. Current major depressive episode as confirmed by the Mini International Neuropsychiatric Interview (MINI)
5. Failure of at least two trials of antidepressant therapy during the current episode
6. Capacity to provide informed consent

Exclusion Criteria:

1. Depression secondary to stroke, cancer or other severe medical illness
2. Major Depressive Episode in people with Bipolar Disorder.
3. Dementia
4. Post-Traumatic Stress Disorder (PTSD)
5. Acute suicidality defined as score ≥3 on HAMD item 3
6. Previous electroconvulsive therapy
7. Known history of intolerance of hypersensitivity to local anesthetic
8. Current substance abuse or dependence (except for caffeine or nicotine dependence) and/or recent history (last 12 months) of current alcohol abuse or dependence, as defined in DSM-5 criteria
9. Unwilling to maintain current antidepressant regimen.
10. A clinical finding/condition that is unstable or that, in the opinion of the investigator(s) would negatively be affected by an SGB (e.g. movement disorder where patient is unable to lie still for injection or anatomical variants making an SGB impractical).

No individual participant data has been planned to be shared with other researchers at this point since this is a feasibility study with only 10 participants.