Inclusion Criteria:  Undergraduate student (ages 18-30) Must own a smartphone Must be able to read and write English  Exclusion Criteria:  Major medical illnesses including diagnosed severe neurological illnesses (e.g., stroke, seizure history), medical conditions associated with neurological effects (e.g. heart, kidney disease), autoimmune disorders, and severe psychiatric diseases (e.g., schizophrenia) Pregnancy History of brain surgery, tumor, intracranial metal implantation, pacemakers or other implanted devices History of adverse reaction to electrical nerve stimulation Prescribed sleep medications and/or psychotropic medications Illicit or prescription drug abuse within the last two months (marijuana or alcohol abuse >2 weeks out will be acceptable for inclusion)