Lighting can affect the health of people in buildings. This goes beyond the safety aspects of providing enough illumination to see by; lighting affects mood and human circadian rhythms, while poor lighting can, in principle, cause glare, headaches, eyestrain, skin conditions and various types of sight loss. This publication reviews existing research on the health effects of lighting (including daylighting) typically found in buildings. It explains medical and psychological research in a clear and accessible way using questions such as: Can LEDs keep you awake at night and damage your brain? Can special lighting help people with dementia?