<P> The term lunar effect refers to real or imaginary correlations between specific stages of the roughly 29.5 - day lunar cycle and behavior and physiological changes in living beings on Earth, including humans . In some cases the purported effect may depend on external cues, such as the amount of moonlight . In other cases, such as the approximately - monthly cycle of menstruation in humans (but not other mammals), the coincidence in timing reflects no known lunar influence . </P> <P> A considerable number of studies have examined the effect on humans . By the late 1980s, there were at least 40 published studies on the purported lunar - lunacy connection, and at least 20 published studies on the purported lunar - birthrate connection . This has allowed several extensive literature reviews and meta - analyses to be produced, which have found no correlation between the lunar cycle and human biology or behavior . </P> <P> Examples of the belief have been found in ancient Assyrian / Babylonian writing . </P>

What effect does the moon have on the human body
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