3. Capacity to provide informed consent to the study
4. PHQ-9 (Patient Health Questionnaire) score of 10-19 at screening
5. Meets criteria for a current major depressive episode (standardised SCID-RV interview)
6. Consents to researchers informing GP (and, if relevant, Local Mental Health Team) of study involvement
You may not be if
1. Currently under, or in need of, the care of mental health crisis (intensive home treatment) services
2. Current mood disorder with psychotic features (SCID-5-RV interview)
3. Current or past diagnosis of bipolar disorder, psychotic disorder, dementia, or mild cognitive impairment, or in the last twelve months alcohol/substance use disorder (SCID-5-RV interview)
4. PHQ-9 suicide item score of greater than one
5. MADRS suicide item score of greater than three
6. Diagnosis of epilepsy or previous seizures or suspected seizures (other than seizures associated with fever with none beyond age five)
7. Active significant skin conditions affecting the scalp, forehead or behind the ears (e.g. psoriasis)
10. Unremovable metal on head, neck or scalp (including unremovable hair extensions that contain metal, metallic piercings or red/orange/pink/yellow tattoos which may contain ferromagnetic dyes), or potential metal fragments in eyes
11. Known or suspected pregnancy (if, on the day, a participant is unsure, they will be given the option to rebook the testing session or to conduct a urine pregnancy test - however, they will be advised that pregnancy tests are only accurate from the first day of a missed period)
12. Medications judged to carry a significant increased risk of seizures
13. Allergies to substances in the tACS paste
14. Major unstable medical illness requiring further investigation or treatment
15. Changes in psychoactive medications in the two weeks preceding screening
16. Involvement in another clinical trial in the past three months, or current involvement in research study or trial that involves an intervention (medication, neuromodulation, psychotherapy)
