With the next full moon approaching on Saturday, July 12, a team of international researchers based in Gothenburg, Sweden, have concluded that people are more sensitive during this lunar phase and will sleep an average of 20 minutes less.
Their results match those of a Swiss study conducted last year involving 33 participants, although the two studies lock horns where REM sleep is concerned.
While the Swiss study says people sleep 20 minutes less during the full moon, it also says they are likely to enjoy 30 minutes more REM sleep, the deepest phase of sleep characterized by rapid eye movements.
The Gothenburg researchers say the brain is more susceptible to external noise distractions when the moon is full, making REM sleep most abundant during the invisible new moon.
"Our study generated findings similar to the Swiss project," says Dr. Michael Smith, who has a PhD in Medical Science from Gothenburg University. "Subjects slept an average of 20 minutes less and had more trouble falling asleep during the full moon phase. However, the greatest impact on REM sleep appeared to be during the new moon."
In Gothenburg, researchers worked with 47 healthy participants between the ages of 18 and 30. They slept in laboratory rooms without windows and were thus unaffected by the light of the full moon.
Although increased cortical reactivity was found in both male and female participants, only the males had trouble falling asleep.
"The purpose of our original study was to examine the way that noise disturbs sleep," Mr. Smith continues. "Re-analysis of our data showed that sensitivity, measured as reactivity of the cerebral cortex, is greatest during the full moon."
Dr. Smith admits the results leave room for speculation, upon which he says it's possible that humans have an inner biological clock that follows the lunar phase, similar to the 24-hour circadian rhythm.
He adds that more highly controlled studies targeting such hypotheses are needed before any concrete conclusions can be drawn.
The study was published in the journal Current Biology.