Bright Light Therapy for Non-motor Symptoms in Parkinson's Disease

Inclusion Criteria: 1. Idiopathic Parkinson's disease diagnosed by neurologist according to the UK Parkinson's Disease Society Brain Bank clinical diagnostic criteria 2. Capable to give informed consent 3. Maintained on stable dose of medications for Parkinson's disease/psychotropic drugs for at least four weeks prior to entry of the study 4. Score 14 or more on the Epworth Sleepiness Scale Exclusion Criteria: 1. A current or past history of manic or hypomanic episode, schizophrenia, mental retardation, or substance use disorder. (Subjects with depression or anxiety disorders will not be excluded) 2. Unstable medical or psychiatric condition 3. Presence of substantial suicidal risk as judged by the clinician and/or screening instruments 4. Presence of active psychotic symptoms that might impair the ability to consent or validity of the interview 5. Cognitive impairment with score of 19 or below by the Hong Kong version of Montreal Cognitive Assessment (HK-MoCA) 6. Contraindication to bright light therapy: history of light induced migraine. Epilepsy, current use of photosensitizing medications, presence of eye disease, e.g. retinal disease, severe cataract, glaucoma and blindness 7. Significant medical condition/ hearing impairment/ speech deficit lead to incapability in completing clinical interview 8. Regular shift worker or trans-meridian flight in the past three months 9. Enrolment in another clinical trial of an investigational medicinal product or device 10. Subjects who are on exogenous melatonin 11. Patients with deep brain stimulation (DBS) implant 12. Patients with known sleep disorders, eg. untreated severe sleep apnea, restless leg syndrome