Light Therapy for Chronic Insomnia in General Practice

receive an active light using glasses of 1500 lux (an average of 180 photons/s/cm2, with a maximum wavelenght at 468 nm), 30-minute long light therapy in the morning, in a time period defined by sleep log and chronotype questionnaire, on a 4-week period

receive a placebo light using glasses (an average of n photons/s/cm2, single- band spectrum with a narrow peak at 660 nm under 50 lux), with the same modality as the experimental group