Melatonin

Melatonin is a hormone that is stimulated by light. It regulates circadian rhythm and helps to cause sleep. It likely has roles beyond these, but these are the primary ones known to modern science.

Melatonin is regulated in the body normally by sunlight and lack thereof. However, with the advent of electricity and the stimulation of bright lights after the sun goes down, much of a modern person’s melatonin regulation deals with exposure to artificial light. It’s debatable that there are yet unrealized, long-term psychological effects behind sleep issues caused by this.

According to some research, “artificial light at night can negatively affect human health, increasing risks for obesity, depression, sleep disorders, diabetes, breast cancer and more.” Some research suggests that certain types of artificial lighting are worse than others in disrupting melatonin production, with bright blue lights being the worst, while light that mimics longer wavelengths like the sun (dark red, orange hues) are the least harmful.