Paper Title
Light Spectrum and Intensity Mitigate Depression among Older Adults

Abstract
Lighting in buildings is one main environmental attribute that plays a significant role in managing behavioral and psychological symptoms through impacting visual and circadian systems. Considering the age-related changes in eyes and the circadian system, specialized lighting design is essential to promote mood and overall well-being in older people. This study aims to evaluate the effects of two whole-day ambient lighting interventions on depression in older adults. Both lighting interventions are designed to create a direct/indirect ambient illumination that provides a high illuminance level (500 lux) in the morning (8:00 – 12:00) and then the illumination is dimmed gradually throughout the day and reached 100 lux in the evening (after 20:00). Using the Geriatric Depression Scale to measure depression levels before, during, and after the lighting interventions, we found a significant decrease in depression after exposure to both lighting conditions; there was more reduction for the L2 intervention. These findings illustrate the beneficial effects of adding varying illumination and spectrum to the ambient lighting quality in residential buildings. Given that older adults spend the majority of their time indoors, designing whole-day ambient lighting with varying intensity and tuning spectrum could be an effective therapeutic solution to lower depression create an antidepressant environment and improve quality of life in older adults. Keywords - Lighting Design, Residential Buildings, Older Adults, Depression