Testing light therapy for movement and thinking symptoms

Inclusion Criteria: * Diagnosis of Parkinson disease Exclusion Criteria: 1. Participants who are unable to comply with study visit/testing requirements (e.g. participants who cannot go off PD medication for the pre-, post-, and 3-month assessments). 2. Participants who are unable to provide consent. 3. Participants with a Deep Brain Stimulation (DBS) device. 4. Participants who have a history of a psychiatric disorder 5. Participants with PD who have other concurrent movement/neurological conditions, including dystonia, dementia, epilepsy etc. 6. Participants with a clinical diagnosis of PD that is not considered primary (e.g. vascular parkinsonism) or participants where an atypical form of parkinsonism is suspected (e.g., progressive supranuclear palsy, multiple system atrophy). 7. Participants with a history of cancer (whether treated with chemotherapy and/or radiotherapy or not). 8. Participants with a history of a recent concussion or any facial, neck, or head injury within the last 6 months. UD IRB Approved: 03/12/2025 IRBNet ID#: 2277769-2 I/C from Rev. 01/2024 Page 3 of 10 Participant's Initial's \_\_\_\_\_\_\_\_ 9. Known injury or disease that might interfere with motor function in the proposed experiments (e.g., stroke, traumatic brain injury, extrapyramidal dysfunction, neuromuscular disease, orthopedic problems that impair movement). 10. Participants with a history of photosensitivity. 11. Participants who are not able to walk unassisted for 2 minutes