According to a new study, sleeping with a light on could have negative health consequences.

While some people prefer to sleep with the TV or lights on, others demand complete darkness in order to get a decent night’s sleep.

Failure to establish a dark environment before night, on the other hand, is not always a harmless preference.

According to a new study published in the Proceedings of the National Academy of Sciences, it has the potential to harm your health in a number of serious ways, including heart disease and cancer.

It took a team of researchers from Northwestern University many months to observe 20 young adults for the study.

Participants in the study were asked to sleep in one of two conditions, which were determined by the researchers.

One night, one group slept in a poorly lit room, followed by another night of sleep in a room with overhead illumination, and so on.

The second group slept in dim lighting for two nights in a row in a dark room.

The findings are shocking and mind-blowing.

“The results from this study demonstrate that just a single night of exposure to moderate room lighting during sleep can impair glucose and cardiovascular regulation, which are risk factors for heart disease, diabetes and metabolic syndrome,” stated senior study author Phyllis C. Zee, M.D., Ph.D., Director of the Center for Circadian and Sleep Medicine and Chief of Sleep Medicine at the Northwestern University Feinberg School of Medicine, in a press release.

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