Sleep Modulation as Antidepressant Randomized Trial

Inclusion Criteria: * Male and female adults aged 18-55 years * Motivated, no aversion against technology * Able to give informed consent as documented by signature, and to follow the technical instructions * Able to understand and speak German or English as required for the interview (HDRS) and to answer the questionnaires * Diagnosis of depression according to DSM-5 criteria (depressed) OR no diagnosis of depression AND no depressive episode in the history (healthy) * ≥17 points in Hamilton Depression Rating Score (HDRS, corresponding to at least moderate-mild depression, depressed) OR \<8 points in HDRS (healthy) * Stable or no pharmacological antidepressant therapy, no acute suicidal tendency (depressed) Exclusion Criteria: * Pregnant or lactating women, women planning to get pregnant during the study period * Bipolar disorder or psychotic symptoms in the history * Relevant disease or medication that could present a risk for the participant or that could influence study findings * Known sleep apnea (diagnosed or ESS ≥10 points) or periodic limb movement syndrome * Known alcoholism or drug abuse * Diagnosed hearing impairment/presbycusis * Irregular intake of centrally depressing or stimulating medication known to alter sleep EEG (e.g., benzodiazepines) * History of traumatic brain injury (except for concussion) or neurosurgical procedures/operations * Known epilepsy or for any reason, intracranial space-occupying lesions or (infectious or autoimmune) inflammatory diseases of the central nervous system * Shift workers * Inability to follow the procedures of the study, e.g., due to language problems, dementia, etc. * Skin diseases/skin problems (in the face/ear/chest area) or allergies that could be aggravated by electrode application * Conditions that may interfere with the MRI (e.g., MR unsafe cardiac pacemaker or a defibrillator, MR unsafe metal in or near the head, spinal cord, eyes, or in the chest) * Indications of sleep apnea (Apnea Hypopnea Index \>15/h) or periodic limb movement syndrome (PLMS index \>15/h) in the screening night * Low stimulation efficiency (\<500 stimulations detected by the device) in the screening night or in 3 subsequent home recording nights, e.g., due to very little deep sleep * Participation in another clinical trial during the study period