Peripheral Neuroimmune Mechanisms of Hyperthermia

Inclusion Criteria:

1. Females and Males ages 18-65
2. English language proficiency
3. Ability to provide informed consent
4. Have a current primary psychiatric diagnosis of major depressive disorder (MDD) of atleast 4 weeks duration, as defined by Diagnostic & Statistical Manual, 5th Edition (DSM-5) criteria using the MINI.
5. Score of ≥ 24 on the Inventory of Depressive Symptomatology - Clinician Rated (IDS-CR)
6. Individuals of childbearing potential must use an acceptable form of birth control.

Exclusion Criteria:

1. Pregnancy or planned pregnancy during study
2. Current breastfeeding
3. History of psychiatric hospitalization within the past year
4. Active suicidal intent ("yes" on item 4 or 5 on the Columbia-Suicide Severity RatingScale)
5. History of bipolar disorder, psychotic disorders, eating disorders, and/or substanceabuse or dependence (within the last year), as per the Mini-InternationalNeuropsychiatric Interview (MINI)
6. Meeting DSM-5 criteria at screening for current obsessive compulsive disorder
7. A ≥25% drop in IDS-CR score from screen (V1) to baseline (V1b)
8. Positive urine toxicology screen due to illicit drug use or other exclusionarymedications. (Potential false positives will be addressed on a case-by-case basis atthe discretion of the investigator)
9. Serious unstable medical condition including cardiovascular, neurological, neoplastic,autoimmune, infectious or endocrine.
10. Morbid obesity (BMI > 40) and/or body shape that might increase the risk of cutaneousburning from the Heckel hyperthermia device (because of truncal skin being too closeto the infrared lights).
11. Any history of or current diagnosis of thrombosis or thrombophilia; if it is unclearwhether a subject has received this diagnosis, a signed release will be obtained tocontact the subject's treating physician and obtain accurate diagnostic information.Depending on the recommendation of the treating physician, the subject may undergoappropriate testing with the treating physician to verify the diagnosis, and if thetests produce negative findings, the subject may be allowed to enter the study
12. Has a history of or an increased risk for gastrointestinal perforation such as ahistory of diverticulitis, stomach or intestinal ulcers or abdominal pain that doesnot go away
13. Using medication that might impact thermoregulatory capacity within 3 days ofreceiving WBH treatment, including: diuretics, barbiturates, beta-blockers,antipsychotic agents, anti-cholinergic agents or chronic use of antihistamines,aspirin (other than low-dose for prophylactic purposes), non-steroidalanti-inflammatory drugs (NSAIDs), systemic corticosteroids, or cytokine antagonists.
14. Use of any medication that could interact in such a way as to potentiate the sedativeeffect of lorazepam or ondansetron, or otherwise deemed unsafe per physician judgment.
15. Fever (Temp > 99) of unknown origin at the time of screen
16. Breast Implants
17. Unsafe cardiac status as defined by abnormal ECG reading at screening visit asdetermined by medical monitor, study doctor, or subject's primary care physician orcardiologist
18. Claustrophobia of sufficient severity to interfere with ability to enter/remain inHeckel device
19. A subject who in the opinion of the Principal Investigator would not be able to safelycomplete the study or would jeopardize study integrity