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Research Review: Light Therapy

Sleep disorders and depression are nonmotor symptoms of Parkinson’s disease (PD) that significantly impact quality of life. In comparison to motor symptoms, there are few effective, evidence-based treatments available for managing these symptoms.


Bright light therapy (BLT) is a well-known treatment for circadian rhythm sleep disorders and seasonal affective disorder. BLT has also been used to treat depressive symptoms and bipolar disorder.


In view of this, a growing body of research is investigating the use of BLT as an alternative treatment for sleep disorders and depression in PD.


Two recent research reviews analyzed the effectiveness of using BLT for improving sleep and depression in people with PD:


The effects of bright light therapy on depression and sleep disturbances in patients with Parkinson's disease: a systematic review and meta-analysis of randomized controlled trials.

July 2021


Data from five randomized controlled trials totaling 173 patients with PD was included.


BLT significantly improved depression symptoms of PD patients. Insomnia symptoms for patients with PD were significantly improved by BLT as well. Whereas, no difference was observed in the control light group in improving the depression or insomnia symptoms of PD patients.


Bright Light Therapy for Parkinson Disease: A Literature Review and Meta-Analysis of Randomized Controlled Trials

November 2021


Six studies were included in the literature review and five randomized controlled trials were included in the meta-analysis.


Despite the positive effects of BLT on PD patients, which were demonstrated in noncontrolled studies, in the meta-analysis of the randomized controlled trials, BLT did not significantly improve the depressive symptoms and excessive daytime sleepiness in PD patients.



Take away: Research suggests that BLT may be an effective treatment for sleep problems and depression in PD, but taken as a whole, studies are not conclusive. The inconsistency between BLT dosage (light timing, intensity and duration) in research studies may impact treatment effectiveness. More research is needed to investigate optimal “dosage” of BLT for people with PD.





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