‘It must be a full moon,’ colleagues remark when a night in the emergency department is particularly blood-soaked or there are an unusual number of psychiatric admissions. It’s an ancient and widespread belief that the moon has a transformative effect on the mind. A 1995 study in the US found that 40 per cent of the general public were convinced the moon had an influence on the mind; an earlier survey put the rate for mental health professionals at 74 per cent. But statisticians haven’t been able to substantiate the claim: the number of admissions for trauma, or for mania or psychosis (‘lunacy’), are unaffected by the phase of the moon, and there is no connection between a full moon and the frequency of suicide attempts, road accidents or calls to crisis support telephone services. My colleagues in emergency medicine, and those 74 per cent of American mental health professionals, are all wrong.
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