• Diagnosis of a schizophrenia-spectrum disorder or mood disorder with psychotic features as determined using the Structured Clinical Interview for the DSM-5
• Less than 5 years since the onset of frank psychotic symptoms as determined using the Symptom Onset in Schizophrenia Inventory
• No evidence of a pre-existing intellectual disability defined as a premorbid IQ >70 as estimated using the Reading subtest of the Wide Range Achievement Test-4
• Ages 15-35
• Non-smoker for past six months
• Absence of suicidal ideation or behavior over the past month as assessed by the Columbia Suicide Severity Rating Scale
• No absolute contraindications to oxygen therapy when indications for oxygen therapy are present according to the American Association for Respiratory Care

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety