Transcranial Direct Current Stimulation Therapy for Sleepiness Related to Shift Work Disorder (tDCS-SWORD)

Inclusion Criteria: * age 18-65 years * works 5 or more night shifts per month (each shift lasting at least 10 hours, with ≥6 hours worked between 10 pm and 8 am) with plans to maintain this schedule for the duration of the 3-week trial * meets the criteria for Shift Work Disorder according to the International Classification of Sleep Disorders24 and evaluation of a sleep medicine provider (physician or nurse practitioner) during a screening evaluation: 1. affirmative answers to Do you experience excessive sleepiness? (yes/no); "Do you experience difficulties with falling asleep during opportunities for sleep? (yes/no); "Is the sleep or sleepiness problem related to a work schedule where you have to work when you would normally sleep? (yes/no)"; and "Has this sleep or sleepiness problem related to your work schedule persisted for at least three months? (yes/no) 2. based on the evaluation of the sleep medicine provider, the sleep and/or wake disturbance are not better explained by another current sleep disorder, medical or neurologic disorder, mental disorder, medication use, poor sleep hygiene, or substance abuse disorder. * Stable medication dosage over previous 4 weeks. * Able to understand English and give a written informed consent document. Exclusion Criteria: * Currently taking stimulant medications such as Modafinil, Armodafinil, Methylphenidate, or Dextroamphetamine. * History of automobile accident due to falling asleep while driving * Inability to understand or read English * Self-reported Substance abuse (current) * Excessive alcohol consumption defined as: * More than 3 glasses of wine a day * More than 3 beers a day * More than 60 mL of hard liquor a day * Presence of cardiac pacemaker or automatic implantable cardioverter-defibrillator (AICD). * Pregnancy, lactation (will be screened with urine pregnancy test) * Non-removable metal or tattoos around head * Use of implantable birth control device such as Implanon * History of frequent severe headaches * Unstable coronary artery disease * Uncontrolled Seizure disorder * Uncontrolled hypertension * Any other clinically significant condition that, in the opinion of the Investigator, might put the subject at risk of harm during the study or might adversely affect the interpretation of the study data.