Parkinson's disease. PD is the second most common neurodegenerative disorder after Alzheimer's disease and affects more than 1% of the elderly population worldwide. Aarsland Påhlhagen Ballard Ehrt Svenningsson 2012. PD is a neuropsychiatric disorder characterized by the cardinal signs of rigidity bradykinesia and tremor. Although motor features define the disorder various non-motor features are typically seen including sleep disturbances, anxiety, and depression. Recent studies have proposed that non-motor complications often carry a greater impact than motor features in PD their recognition is often the key to the successful treatment of a Parkinson patient Simuni Sethi 2008. The core of PD management is symptomatic treatment with drugs, however, long term treatment of this array of symptoms with various drugs causes the occurrence of adverse short and long term side effects such as dyskinesia and psychosis Kalia Lang 2015. These side effects reflect the importance of implementing non-invasive treatments to reduce the total daily dose of dopamine replacement Willis Moore Armstrong 2012. On this basis, bright light therapy BLT has been proposed as the treatment of choice for seasonal affective disorder and was also shown to be effective in the improvement of depression, anxiety, insomnia and the motor symptoms associated with PD Willis Turner 2007. Despite the established therapeutic potential of BLT in seasonal depression and potential usefulness across a wide array of applications considerably less is known about the efficacy of BLT in treating both non-motor and motor symptoms in more advanced patients the side effects and tolerability of BLT in populations with PD. Thus this may restrict the depth of understanding of the efficacy of BLT in patients with PD.
