The purpose of this research study is to use a specific type of non-invasive brain stimulation known as transcranial alternating current stimulation (tACS) to determine its effects on brain activity (measured with EEG) and mood in patients with Major Depressive Disorder (MDD).

The device used for non-invasive brain stimulation is investigational and has not been approved by the FDA, though it has been designated as a nonsignificant risk (NSR) device study by the FDA. Half of the participants will receive tACS and half will receive sham stimulation, an inactive control procedure for comparison use only. Participation in this study includes up to eight appointments, each one lasting from 30 minutes to four hours over the course of 3 weeks. The first two appointments will be remote interviews to determine eligibility. If the subjects qualify, the next five appointments will be scheduled as consecutive stimulation sessions in the Carolina Center for Neurostimulation at the Vilcom office. The follow-up appointment will be in our center two weeks after the completion of the stimulation sessions. We estimate the total time needed to complete study participation to be about 17 hours.

Inclusion Criteria:

• Ages 18-70 years
• DSM-IV diagnosis of MDD; unipolar, non-psychotic
• Hamilton Rating Depression Rating Scale (HRDS-17) score >8
• Low suicide risk as determined by a score of <3 on the Suicide Item on the HDRS-17 and based on additional information from the C-SSRS (no intent)
• Capacity to understand all relevant risks and potential benefits of the study (informed consent)

Exclusion Criteria:

• DSM-V diagnosis of moderate or severe alcohol use disorder (AUD) within the last 12 months.
• DSM-V diagnosis of moderate to severe substance use disorder (excluding tobacco) within the last 12 months.
• Current axis I mood, or psychotic disorder other than major depressive disorder
• Lifetime comorbid psychiatric bipolar or psychotic disorder
• Eating disorder (current or within the past 6 months)
• Obsessive-compulsive disorder (lifetime)
• Post-traumatic stress disorder (PTSD, current or within the last 6 months)
• Change of ADHD medication within the last 4 weeks.
• Change of benzodiazepines or anti-epileptic medication within the last 4 weeks
• Antidepressant drugs taken for less than 4 weeks (i.e., recently initiated)
• Neurological disorders, including but not limited to history of seizures (except childhood febrile seizures and ECT-induced seizures), dementia, history of stroke, Parkinson's disease, multiple sclerosis, cerebral aneurysm.
• Medical or neurological illness (unstable cardiac disease, AIDS, malignancy, liver or renal impairment) or treatment for a medical disorder that could interfere with study participation; comorbid neurological condition (i.e. seizure disorder, brain tumor)
• History of traumatic brain injury that required subsequent cognitive rehabilitation, or cause cognitive sequelae.
• Prior brain surgery and/or any brain devices/implants, including cochlear implants and aneurysm clips
• Current pregnancy or lactation. If the ability to become pregnant exists, unwillingness to use appropriate birth control measures during study participation
• Anything that, in the opinion of the investigator, would place the participant at increased risk or preclude the participant's full compliance with or completion of the study
• Non-English speakers

IPD will be shared upon request.

Data will be available starting from 9 to 36 months following publication.

Deidentified individual data that supports the results will be shared beginning 9 to 36 months following publication provided the investigator who proposes to use the data has approval from an Institutional Review Board (IRB), Independent Ethics Committee (IEC), or Research Ethics Board (REB), as applicable, and executes a data use/sharing agreement with UNC.

Adverse Events were assessed at Day 1, Day 2, Day 3, Day 4, Day 5 and 2-week follow-up

Using sham stimulation.