Researchers found evidence of a "lunar influence" in a study of 33 volunteers sleeping in tightly controlled laboratory conditions.
When the Moon was round, the volunteers took longer to nod off and had poorer quality sleep, despite being shut in a darkened room, Current Biology reports.
They also had a dip in levels of a hormone called melatonin that is linked to natural-body clock cycles.
When it is dark, the body makes more melatonin. And it produces less when it is light.
Being exposed to bright lights in the evening or too little light during the day can disrupt the body's normal melatonin cycles.
But the work in Current Biology, by Prof Christian Cajochen and colleagues from Basel University in Switzerland, suggests the Moon's effects may be unrelated to its brightness. (+ video) » | Michelle Roberts | Health editor | BBC New Online | Thursday, July 25, 2013
