Exploring Mechanisms for Neuropsychiatric Symptoms of Parkinson Disease Using Transcranial Direct Current Stimulation

Inclusion Criteria: * Abel to provide written informed consent is obtained in the English language * Age 18 to 95 years old * Movement Disorder Society Clinical Diagnostic Criteria for probable idiopathic Parkinson disease * Report disabling depressive or neuropsychiatric symptoms prior to study entry * Capacity to understand the nature of the study; Exclusion Criteria: * Known structural brain disease such as a neoplasm, abscess etc. * Pre-existing skull / scalp defects that would impede standardized electrode placement * Current electronic or metal implants * Diagnosis of Bipolar Disorder, Post-Traumatic Stress Disorder, a Psychotic Disorder or any other non-unipolar depressive disorder as a principal diagnosis in the 6 months prior to screening; * Concurrent treatment with medication which may affect tDCS (benzodiazepines, anticonvulsants, dextromethorphan and pseudoephedrine) * Endorse active suicidal ideation at enrollment or during any study visit, or have attempted suicide in the six months prior to screening; * History of substance abuse or dependence in the 2 months prior to screening; * Considered to be at significant risk of committing homicide; * Unstable medical condition; * Score less than 22 on the Montreal Cognitive Assessment (MoCA) * Women of childbearing potential who are pregnant or are considering becoming pregnant during the length of the study; * There has been a change in their depression or psychotherapy treatment regimen in the 2 weeks preceding screening;