Circadian Rhythm Phase Advance with Dawn Simulation Treatment for Winter Depression

A naturalistic pattern of dawn simulation (93 min, 0.001-250 lux) delivered to sleeping patients with winter depression has clinical efficacy similar to postawakening bright light therapy. The authors tested the circadian phase-shifting capacity of the dawn signal in a placebo-controlled, randomized 3-week field trial using 4 photic or nonphotic comparators: 30-min, 10,000-lux bright light therapy; a 13-min, 250-lux light pulse at the end of sleep; and high- and low-density negative air ionization timed to match the dawn. Bright light and dawn treatments both produced average phase advances of similar to 30 min, while the pulse and ion exposure had minimal effect. The authors conclude that very dim, incremental levels of light at the end of the night, with a dominant red component through eyelid filtering, facilitate circadian rhythm phase advances, possibly in conjunction with room light after awakening.