Transcranial Direct Current Stimulation (tDCS) for Treatment of Substance Use Disorder

Inclusion Criteria: * Ability to understand and give informed consent * Men and women 18-60 years of age. * For women of childbearing potential, current use of a medically acceptable form of birth control * DSM-5 diagnosis of stimulant use disorder with crack/cocaine as the drug of choice or opioid use disorder Exclusion Criteria: * Lifetime diagnosis of schizophrenia, schizoaffective disorder, schizophreniform disorder, bipolar I disorder, or delusional disorder as confirmed by the MINI or autism spectrum disorder as confirmed by medical history at the screening visit * Current clinically significant or unstable medical conditions, including metabolic, endocrinological, oncological or autoimmune diseases, infectious diseases common in people with substance use disorders including Hepatitis B and C or HIV/AIDS; use of medications deemed exclusionary by the study team; or any laboratory value outside the reference range that the senior investigator team considers to be of clinical relevance * Head trauma with loss of consciousness (\>30 min) * History of neurological or developmental disease of central origin including stroke, brain tumor or seizures, encompassing those symptoms associated with periods of drug withdrawal or abstinence * Metal implants or devices that may be impacted by the electrical stimulation and additional MR contraindications * Women of childbearing potential must use a medically acceptable birth control method during the study and will be asked to take a pregnancy urine test before exposure to tDCS (or MRI)