Sleep Modulation as Antidepressant Randomized Trial (SMART)

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