Trial Parameters
Brief Summary
To evaluate the acute and sustained antidepressant effects of nitrous oxide in people with major depressive disorder; and further evaluate these effects by identifying the optimal dose and regimen to guide current practice, and to plan a future large pragmatic trial.
Eligibility Criteria
Inclusion Criteria: 1. Adult (≥18 years, both sexes) 2. DSM-5 criteria for MDD without psychosis, as determined using a structured clinical interview \[Mini International Neuropsychiatric Interview\], MDD, defined by a pre-treatment score \>16 on the HDRS-21 scale and meeting DSM-5 for MDD Exclusion Criteria: 1. A current or past history of bipolar disorder, schizophrenia, or schizoaffective disorder. 2. Current obsessive-compulsive disorder, panic disorder, or documented Axis II diagnoses 3. Active suicidal intention, as determined by clinical interview assessment tool (Sheehan-STS) and clinical examination 4. Active or recent (\<12 months) substance use disorder; excluding nicotine 5. Administration of NMDA-antagonists (e.g., ketamine) in previous 3 months 6. Ongoing treatment with ECT 7. Presence of acute medical illness that could interfere with study participation, including significant pulmonary disease 8. Pregnancy or breastfeeding 9. Any contraindications to the use of nitrous