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We investigated the effectiveness of morning blue light in advancing the sleep and melatonin rhythm of individuals with mild delayed sleep phase syndrome.


The 18 participants were randomly allocated to a light or control group. Wake-up times were gradually advanced to 06.00 over a week, during which the light group also received two hours of blue light immediately after waking. During the treatment week that followed, the blue light group was exposed to two hours of blue light each morning, starting immediately after waking up. The portable light source comprised blue light LEDs (470 nm peak wavelength with irradiance of 65 μW/ cm2) attached to the lower rims of spectacle frames.


The blue light group showed a significant 2.53-h advance of dim light melatonin onset, compared to no change in the control group. However, neither group had a significant advance of sleep times following treatment. Effective delayed sleep phase syndrome treatment may require adjunct behavioral instructions.

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