To measure the effects of Microbial Ecosystem Therapeutics (MET)-2 on symptoms of depression and anxiety using pre- and post-treatment scores for overall depression and anxiety

An eight week, randomized, placebo controlled trial to assess subjective changes in mood and anxiety symptoms from baseline to after MET-2 treatment in participants with depression, using MADRS, Hamilton Anxiety Rating Scale (HAM-A), and other mood/anxiety scales and to demonstrate a significantly higher proportion of responders in patient who were randomized to receive the active study drug compared to patients who were randomized to receive placebo.

Inclusion Criteria:

1. Able to provide informed consent.
2. Not pregnant
3. Willing to participate in follow up as part of the study
4. Diagnosis of Major Depressive Disorder (MDD) by the Mini-International Neuropsychiatric Interview (MINI)
5. Current depressive episode with a Montgomery-Asberg Depression Rating Scale (MADRS) score of ≥15.
6. Able to understand and comply with the requirements of the study
7. Able to provide stool, urine, and blood samples.
8. Those who do not choose to use antidepressants for moderate-severe depression.

Exclusion Criteria:

1. History of chronic diarrhea
2. Need for regular use of agents that affect gastro-intestinal (GI) motility (narcotics such as codeine or morphine, agents such as loperamide or metoclopramide)
3. Colostomy
4. Elective surgery that will require preoperative antibiotics planned within 6 months of enrolment
5. History of bariatric surgery.
6. Pregnant, breastfeeding, or planning to get pregnant in the next 6 months
7. Any condition for which, in the opinion of the investigator, the participant should be excluded from the study.
8. Current use of any antidepressant/antianxiety drug (eligible to participate after a 4-week washout period)
9. More than three depressive episodes throughout lifetime
10. Having failed an anti-depressant treatment during current depressive episode
11. Use of any antibiotic drug in the past 4 weeks (may be eligible to participate after a 1-month washout period)
12. History of alcohol or substance dependence in the past 6 months
13. Daily use of probiotic product in the past 2 weeks (may be eligible to participate after a 2-week washout period)
14. Use of any type of laxative in the last 2 weeks.
15. Consumption of products fortified in probiotics (may be eligible to participate after a 2-week washout period)
16. High suicidal risk, as measured by MADRS item 10 score more than 3
17. Current psychotic symptoms
18. Bipolar Depression
19. History of epilepsy or uncontrolled seizures
20. Immunodeficiency (immuno-compromised and immuno-suppressed participants; e.g. acquired immune deficiency syndrome [AIDS], lymphoma, participants undergoing long-term corticosteroid treatment, chemotherapy and allograft participants)
21. Unstable medical conditions or serious diseases/conditions (e.g. cancer, cardiovascular, renal, lung, diabetes, psychiatric illness, bleeding disorders, etc.)
22. The use of natural health products (NHP); e.g. St. John's Wort, passion flower, etc.) that affect depression
23. History of Electroconvulsive therapy (ECT)

Hospital pharmacies will be provided with the randomization code and will dispense the appropriate medication to subjects. A fire-wall exists between the pharmacies and the investigational staff.