Dr. Daniel Kripke explains why light therapy can correct certain kinds of insomnia. Delayed Sleep Phase Syndrome Resource pages for people who fall asleep late and wake up late. Light Therapy Light therapy for Delayed Sleep Phase Syndrome. JAMA light therapy applications to depression, jet lag, and circadian rhythm sleep disorders. To read more about the effects of sleep disorders and sleep deprivation, visit Mind over mattress and Triggers survey results .
Light brightness is measured in lux.
Outside on a sunny day, the brightness level is about 10,000 lux. In the shade, the brightness goes down to 3,000 lux. Indoors, the level drops to 200 lux, and in front of the TV with the lights dimmed, the brightness is only 10 lux. If we spent most of the day outside like our ancestors, our body clocks would be set normally.