Inclusion Criteria:
1. Outpatient youth between the ages 10-17 years
2. Children's Yale-Brown Obsessive-Compulsive Scale (CY-BOCS) ≥16 (moderately severe). OCD must be determined to be the primary or co-primary diagnosis using the The Schedule for Affective Disorders and Schizophrenia for School-Age Children- Computer administered version (KSADS-COMP) based on all available information.
3. Child has a full-scale IQ≥85 as assessed on the Wechsler Abbreviated Scale of Intelligence® Second Edition (WASI®-II) (within 90% CI). To decrease participant burden, the WASI®-II will only be conducted in cases of suspected intellectual disability after meeting with the PI.
4. English speaking.
Exclusion Criteria:
1. Receiving concurrent psychotherapy for subject's OCD (except maintenance).Subjects receiving pre- established concurrent psychotherapy for at least 8 weeks regarding other psychological issues are eligible for enrollment.
2. New Treatments: Initiation of an antidepressant within 12 weeks before study enrollment or an antipsychotic 6 weeks before study enrollment. No new alternative medications, nutritional or therapeutic diets within 6 weeks of study enrolment.
3. Established Treatment changes: Any change in established psychotropic medication (e.g., antidepressants, anxiolytics, stimulant, alpha agonist) within 8 weeks before study enrollment (6 weeks for antipsychotic). Alternative medications must be stable for 6 weeks prior to baseline. Any medications must remain stable during treatment; consistent with the National Institute of Health (NIH)-funded Child Anxiety Multimodal Study (CAMS) trial, downward adjustments due to side effects may be acceptable and will be discussed with the study child and adolescent psychiatrist and the community psychiatrist.
4. Current clinically significant suicidality or individuals who have engaged in suicidal behaviors within 6 months will be excluded and referred for appropriate clinical care.
5. Meets Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V) criteria for conduct disorder, autism, bipolar, attention deficit hyperactivity disorder (ADHD), Tourette's syndrome, schizophrenia or schizoaffective disorders
6. Youth with hoarding symptoms as they may be conceptually and genetically different from other OCD subtypes.
7. BMI less than 18.5.
8. Contraindication to tDCS: history or epilepsy, metallic implants in the head and neck, brain stimulators, vagus nerve stimulators, ventriculoperitoneal (VP) shunt, pacemakers.
9. Active substance dependence (except for tobacco).
10. Pregnant or nursing females as the effects of tDCS on pregnancy are unknown.
11. Presence of a significant and/or unstable medical illness that might lead to hospitalization during the study.
