A study conducted by US researchers confirmed higher melatonin levels and better quality sleep after just a few weeks of regular exposure to natural light during the day.

Increased exposure to natural light during the day attenuates the circadian system’s evening photosensitivity and reduces negative effects on melatonin production

The research compared the effects of two different light exposure regimen on participants’ melatonin production: one week with high exposure to daylight – around 4 hours in bright light (daylight or light coming through light boxes indoors), and a second week with low exposure, where participants wore glasses transmitting 2% of light outside and spent only one hour outside. Melatonin levels were then measured from saliva samples of the research participants.

The results showed that after a week of low light exposure, melatonin production was significantly more suppressed in participants exposed to ‘intrusive night light’ compared to a week of high exposure where the participants spent several hours a day in bright light. The research confirmed that the photosensitivity of the circadian system, and therefore melatonin production and sleep quality, are affected by the length of daily light exposure and its intensity over the past few days or weeks.