Please assess the completion status of the following clinical trial:

Trial Title: NMDA Receptor Antagonist Nitrous Oxide Targets Affective Brain Circuits

Study Design Characteristics:
- Allocation: RANDOMIZED
- Intervention Model: CROSSOVER
- Observational Model: None
- Primary Purpose: TREATMENT
- Time Perspective: None
- Masking: DOUBLE
- Phase: PHASE1
- Number of Arms: 2.0

Eligibility Criteria:
Inclusion Criteria:~* Adults 18-65 years of age~* Right-handed~* Controls: Not meet The Fourth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for major depressive disorder (MDD) by scoring ≤7 on the Hamilton Depression Rating Scale (HDRS), 17-item; Treatment-Resistant Major Depression (TRMD) patients: Must meet a ≥17 score on the HDRS.~* Controls: Must not have any history of depression as determined by reported history and medical record review; TRMD: Documented (chart review) failure to respond to ≥3-4 adequate dose/duration antidepressant treatments; ≥1 in the current depressive episode.~* Good command of the English language~Exclusion Criteria:~* Meets criteria for any DSM-IV Axis I diagnosis as documented in medical records and as determined by structured clinical interview (except MDD for the TRMD group)~* Known primary neurological disorders or medical disorders including dementia, stroke, encephalopathy Parkinson's Disease, brain tumors, multiple sclerosis, seizure disorder, severe cardiac or pulmonary disease~* Any central nervous system active medication as determined by study investigator~* Any known disease affecting drug metabolism and excretion (e.g. renal or liver disease) as determined by study investigator~* Left-handedness~* Not eligible for MRI scans (e.g. history of claustrophobia/implanted metal as per MRI Screening Tool)~* Current use of psychotropic medications, antidepressants, or prescription or non-prescription drugs/herbals intended to treat depression or anxiety (control group only)~* Any recent (within past 12 months) history of substance dependence or abuse, determined by reported history or urine drug screen~* Ability to become pregnant and not using effective contraception~* Contraindication against the use of nitrous oxide:~  1. Pneumothorax~ 2. Bowel obstruction~ 3. Middle ear occlusion~ 4. Elevated intracranial pressure~ 5. Chronic cobalamin and/or folate deficiency treated with folic acid or vitamin B12~ 6. Pregnant patients~ 7. Breastfeeding women~* Inability to provide informed consent~* Any other factor that in the investigators' judgment may affect patient safety or compliance (e.g. distance greater than 100 miles from clinic).

- Gender: ALL
- Minimum Age: 18 Years
- Maximum Age: 65 Years
- Healthy Volunteers: t

Study Arms:
- Nitrous Oxide (Type: EXPERIMENTAL): One hour inhalation of nitrous oxide
- Placebo Gas (Type: PLACEBO_COMPARATOR): One hour inhalation of placebo gas

Based on this trial design, predict the completion outcome and termination type (if applicable).