The investigators are investigating whether home-based tDCS over the course of four weeks can improve ADHD symptom severity and improve dysexecutive functioning (cognitive control). Further, the investigators are investigating whether there is a dose-dependent response to tDCS.
Inclusion Criteria: 1. Male and female outpatients 18-65 years of age 2. A diagnosis of ADD/ADHD or meeting the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria. Exclusion Criteria: 1. Contraindication to tDCS: history or epilepsy, metallic implants in the head and neck, brain stimulators, vagus nerve stimulators, VP shunt, pacemakers, pregnancy. 2. Active substance dependence (except for tobacco). 3. Pregnant or nursing females. 4. Inability to participate in testing procedures. 5. Premorbid neurological conditions (including neurovascular and neurodegenerative diseases such as traumatic brain injury, stroke, Parkinson's, AD and other dementias) and severe psychiatric disorders (bipolar disorder, schizophrenia).