Multi-site Feasibility of an Integrated Treatment for the Biology and Experience of Depression: The MULTIBED Study

Inclusion Criteria: * 18 years or older * Able to read and speak in English * Able to understand the nature of the study and able to provide written informed consent * Current major depressive episode of at least 2 weeks duration as assessed by the Structured Clinical Interview for DSM-5 (SCID) and a Patient Health Questionnaire - 8 (PHQ-8) score of 10 or greater at screening * Willing to use a form of pregnancy contraceptive (e.g., barrier methods such as condoms, oral contraception, or other birth control type) if assigned female sex at birth and premenopausal * Able to lie supine for 2 hours in a sauna device * Access to the internet via computer, smartphone, or tablet Exclusion Criteria: * \>30% reduction in BDI-II score between Screen #1 and Screen #2 (conducted \~1 week after Screen #1) * Suicide attempt in the past 12 months defined using the SAMHSA suicidality question during the clinician-administered interview or active suicidal ideation as indexed by a score of 3 on the BDI-II suicidality item during the clinician-administered interview * Any of the following medical conditions: cardiovascular disease (other than controlled hypertension), seizure disorder, history of cerebrovascular accident (CVA) or other serious neurological condition (e.g. Parkinson's disease, multiple sclerosis, or dementia), current neoplasia, any active enclosed infection (e.g. dental abscess, joint infection), hemophilia or other cause for excessive bleeding (e.g. platelet disorder), or o…