Getting a good night's sleep is not as easy when the full moon is shining, a study has found.
A sleep researcher from the University of Basel, in Switzerland, has found evidence that the various phases of the moon - particularly the full moon - can determine how well we sleep at night.
Dr Christian Cajochen examined the sleeping patterns of 33 people earlier assessed in a sleep clinic.
Information on the individual brain activity found that those who had had poor sleep were those who were assessed during a full moon phase.
"Around a full moon, people had less deep sleep - about 30 per cent less sleep," Dr Cajochen said. "They slept, in general, 20 minutes less and it took them five minutes longer to fall asleep."
The full moon has been the subject of myths, legends and folklore in different cultures around the world.
One of the best-known legends is of the werewolf - a person who, when the moon is full turns into a wolf-like creature.
Other cultures associate the full moon with curses, magic, witchcraft and lunacy.
Dr Cajochen said he was "very sceptical" about the idea that one got less sleep on a full moon until he saw the research data.
The people who took part in the sleep assessments had all been in the same kind of room, which was completely dark and from which the moon was not visible.
Dr Cajochen said the fact that a person's sleeping pattern could be affected by the phase of the moon indicated that humans had a lunar body clock.