Nitrous Oxide as a Putative Novel Dual-Mechanism Treatment for Bipolar Disorder
Nitrous Oxide as a Putative Novel Dual-Mechanism Treatment for Bipolar Disorder
This study is a 7-day randomized, double-blind proof-of-concept pilot study of nitrous oxide vs. midazolam in 40 adults (20-60 years) with bipolar disorder (BD) (type I or II). Ongoing pharmacological and psychosocial treatments may continue, provided that they have not been initiated or significantly modified in the preceding 2 weeks. Participants' current treatment as prescribed by clinical psychiatrists will not be modified or interfered in this study. The study involves 3 visits. During study visit 1, participants will complete screening to ensure study eligibility. This will be done using interview measures. During study visit 2, participants will complete anthropomorphic measurements, measurement of endothelial function, screening blood work, ECGs, and an anaesthesia screener. During study visit 3, participants will receive the treatment (nitrous oxide or midazolam), complete an MRI scan, and complete interview measures and self-reports. There will be anthropomorphic measurements taken as well. The participant will be required to complete phone interviews and self-reports over the subsequent 7 days. There are 4 main predictions: 1. Nitrous oxide will significantly reduce depression symptoms vs. midazolam. 2. Nitrous oxide will significantly increase frontal cortical perfusion vs. midazolam. 3. Lower perfusion in frontal cortical regions at baseline will be associated with greater improvement in depression symptoms following nitrous oxide treatment. 4. Poorer endothelial function will be associated with greater improvement in depression symptoms following nitrous oxide treatment.
Inclusion Criteria:
English-speaking; age 20-60 years; BD-I or BD-II, current major depressive episode ≥4 weeks duration; MADRS≥22; taking ≥1 mood stabilizing medication/s (i.e. antimanic anticonvulsant, antipsychotic, and/or lithium).
Exclusion Criteria:
New medications or changes in dosing, or ECT or TMS, in the preceding 2 weeks; MADRS item 10, > 4; YMRS≥12; acute significant suicidality; psychosis; substance abuse (past 3 months); active major medical conditions (hepatic, renal, respiratory, or cardio/cerebrovascular disease; diabetes; esophageal reflux; sleep apnea); B12 deficiency/disorders; pregnant; MRI contraindications; history of adverse anaesthetic reactions; anaesthesia class >2; scuba diving in preceding week.