Bad Moon Rising: the persistent belief in lunar connections to madness.

S ix patients walk into the emergency department asking for opiates while 3 code blues are announced on the PA. Someone mutters , " Damn! It must be a full moon! " The belief that the moon exerts an influence on human affairs has survived rather obstinately through history. Hippocrates wrote that " no physician should be entrusted with the treatment of disease who was ignorant of the science of astronomy. " 1 Even when, in the 17th century, Jo-hannes Kepler caused the disciplines of astrology and astronomy to diverge with his discovery that the motions of the planets followed mathematical laws, the belief in the moon's influence lingered. And lingered it has to this day. A study by Rotton and Kelly in 1985 showed that 50% of university students believed that people act strangely during a full moon. 2 In 1995, Vance reported that as many as 81% of mental health professionals believed that the full moon alters individual behaviour. 3 In the popular imagination, lunar influences on the human mind are often ascribed to the moon's gravitational effects. Not everyone realizes that, although the moon is able to move oceans, this is achieved only because the moon's gravity acts over the 12 800-km diameter of the earth, which pulls back with a comparable force. But the moon exerts no influence on smaller bodies of water such as lakes and even some seas, and the difference between a person's weight in the presence of the moon's gravity and his or her weight if there were no moon is " less than the effect of a mosquito on one's shoulder. " 4 It is also important to realize that these gravita-tional forces are dependent on the distance between the earth and the moon, and on the alignment of the sun, earth and moon, and not on the phases of the moon. The observations made by Galileo Galilei of the phases of the moon remain correct in today's astronomical understanding. There are 8 phases of the moon, which succeed each other with a periodicity of 3.69 days: new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, waning crescent. Astronomy also defines 5 different lunar cycles based on different parameters of time and distance from the earth: tropical, draconic, sidereal, anomalistic and synodic — the synodic cycle being the interval between 2 successive new moons. This is the time …