Your tossing and turning might not be about that stressful situation at work after all. It may the moon keeping you up at night. A new study in the journal Current Biology said people get lower quality sleep at the time of a full moon — an average of twenty minutes less than they do during a new moon.

But the disruption doesn’t come from light exposure, as you might expect. Researchers from the Psychiatric Hospital of the University of Basel (Baaah-Sel) discovered that the human body knows what’s going on in the sky … even behind closed doors. Thirty-three volunteers between the ages of 20 and 74 were kept in a laboratory with no windows or way of seeing the moon for three and a half days. The participants, who had no idea the moon would be part of the study, took about five minutes longer to fall asleep around the time of a full moon compared with how long it took them to slip into dreamland during the following new moon. This phenomenon seems to cause energy levels to wax and wane, too.

The full moon deprived the lab participants of an average of twenty minutes of sleep — and even led to a decrease in bodily levels of melatonin — a hormone important in regulating the body’s wake and sleep functions. Researchers said further research has to be completed to confirm the assertions. But the study is enough to make you wonder why you woke up on the wrong side of the bed.

According to experts, a chronic lack of sleep can lead to depression, heart disease and even weight gain. About 90 percent of people who suffer from insomnia faced other health problems like stroke, high blood pressure and diabetes.

This November, which is National Sleep Comfort Month, we’ll see the full moon on the seventeenth. So if the study holds true — that Monday after the full moon on November 18 may prove to be one of your worst cases of the Mondays yet.