How does the moon cycle effects human sleep? Anecdotal evidence has long suggested that human sleep patterns, menstrual cycle, moods, and even aggression are linked to moon cycles. A research paper published in Current Biology in 2013 showed that there exists a correlation between the human sleep cycle and lunar phases. Researchers from the Psychiatric University Hospital in Switzerland studied 33 volunteers in a laboratory environment while they slept. The group was split evenly among men and women and included both young adults between 20 and 31 years old and individuals in the 57-74 age groups. The same types of sleep patterns were witnessed in both groups, although some impacts were more pronounced in the young because older adults typically sleep less deeply than their younger counterparts. They found a striking association between poor sleep and lunar cycles. In the few days before and after a full moon, people took an average of 5 extra minutes to fall asleep, slept 20 minutes less per night, and had 30 per cent less deep sleep, as measured by the electroencephalograms. Moreover, the people recorded poorer sleep on a survey around the full moon. These changes were associated with a decrease in subjective sleep quality and diminished endogenous melatonin levels (the hormone that induces sleep). The researchers point out that the moon’s effects may vary across the population.