22 August 2006
B-1 Light quality and quantity can have profound physical and psychological effects.
In addition to the eye fatigue that can be caused by direct and reflected glare, lighting
also affects Seasonal Affective Disorder (SAD), sleep disorders, and jet lag.
B-1.1 Seasonal Affective Disorder (SAD) is a clinical condition brought about by the
shorter days and less sunlight during fall and winter seasons. Symptoms include a loss
of physical energy as well as emotional depression, increase in sleep requirements, and
an increase in appetite. Light therapy has been used to treat SAD where patients are
exposed to levels of light significantly higher than those typically provided indoors. The
therapy depends more on the quantity of light, than the light source. Introducing
daylight into interior spaces is the best architectural solution for SAD.
B-1.2 Sleep disorders. Because of the connection between light and sleep cycles,
scientists expect that light therapy can be used to treat some sleep disorders. However,
no recommendations have yet been developed for such therapy. Because circadian
cycles depend on daylight during the day and darkness while sleeping, it is extremely
important to expose people to daylight during the day and eliminate or minimize light in
B-1.3 Jet lag results in a variety of symptoms ranging from sleep disruption to digestion
problems. Similar to sleep disorders, scientists expect that light therapy can be used to
overcome jet lag and its negative effects faster than the natural adjustment period.