Society for Light Treatment and Biological Rhythms Annual Meeting. 1993; 4:11

CIRCADIAN PHASE-SHIFTING EFFECTS OF "DIM" GREEN LIGHT

Alfred Lewy, Saeeduddin Ahmed, Vance Butler, Neil Cutler, Murray Waldman*, and Robert Sack

Sleep and Mood Disorders Laboratory, OHSU L-469, Portland OR 97201 *Sunnex Biotechnologies, Winnipeg Canada R3B 1Y6

Seven subjects diagnosed with winter depression participated in a seven-week double-blind placebo controlled crossover protocol. Green light intensity was 200 lux for the first year (N= 5) and 400 lux for the following year (N= 2), relatively "dim" compared to the 2500 lux white light used in previous studies.

The experimental design was similar to that of previous bright white light studies. The study was comprised of a baseline week, two weeks of AM or PM light, a washout week, and a final two weeks of crossover treatment (AM or PM light). The order of treatments was randomly assigned. DLMOs were obtained at the end of appropriate weeks. Subjects were interviewed at the end of each week using the SIGH-SAD rating scale.

No significant behavioral results were found. However, analysis (two-tailed paired t-tests) of the 29-item SIGH-SAD psychological data indicates that patient depression ratings decreased after morning light compared to the baseline week prior to treatment( p< 0.07) and compared to ratings after evening light (p< 0.31)

Analysis of the physiological data (two-tailed paired t-tests) indicates that patients are significantly (p< 0.026) phase advanced after two weeks of morning green light exposure as compared to the baseline week prior to treatment. Patients are also significantly (p< 0.0028) phase delayed after two weeks of evening light exposure as compared to the baseline week prior to treatment. A direct comparison between second light treatment weeks indicates that after two weeks of morning light, patients are significantly (p< 0.028) phase advanced compared to their delayed phase position after two weeks of evening light.

When comparing these DLMOs to those previous subjects exposed to 2500 lux bright white light (N= 23), DLMO averages were nearly identical except for the morning light comparisons. Perhaps a larger N is needed to sustantiate that 200-400 lux green light produces phase shifts (particularly phase advances) similar to those produced by 2500 lux white light.

Note: Sunnex Biotechnologies funded this study and has submitted a patent application.

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