Eighty per cent of nurses believe psychological disorders are more prevalent during the full moon, which the Montreal study says is not the case. (Gary Hershorn/Reuters)

The long-held view that a full moon or even a new moon triggers psychological problems has been debunked by a study from Montreal.

Researchers at the University of Laval's School of Psychology evaluated patients visiting Montreal's Sacré-Coeur Hospital and Hôtel-Dieu de Lévis between March 2005 and April 2008 and found no correlation between anxiety disorders and the phases of the moon — despite, it seems, what 80 per cent of nurses and 64 per cent of doctors surveyed believe.

These researchers analyzed 771 individuals who had shown up at the emergency room with chest pains for which no medical cause could be determined.

Psychological evaluations indicated many were suffering anxiety, panic attacks, mood disorders or suicidal thoughts. The time of their visit was then correlated with the phase of the moon at that moment.

"We observed no full-moon or new-moon effect on psychological problems," said lead researcher Genevieve Belleville whose study is published in General Hospital Psychiatry.

The study went on to suggest that health professionals may think there are more mental problems during a full-moon phase due to "self-fulfilling prophecies."

These are the moon phases:

• New moon: when the moon is positioned between the earth and the sun, so the dark side of the moon is facing us.
• Full moon: when the earth, moon and sun are in approximate alignment and the moon is on the opposite side of the earth so the lit-up side of the moon is facing us.
• First quarter and third quarter moons: also known as half moons happen when the moon is at a 90-degrees in relation to the Earth and the sun so, half of the moon is shadow and half is illuminated.

According to the study, there is no link between incidences of psychological problems and the four lunar phases, with one exception: for some reason anxiety conditions dropped by 32 per cent during the last lunar quarter.

"This may be coincidental or due to factors we did not account" for, said Belleville.

Belleville said the study was done to "put the idea to rest" among many health professionals who believe a full moon exacerbates mental conditions. Belleville points out that 80 per cent of nurses and 64 per cent of doctors surveyed in her study believe this to be the case.

"This misperception could … colour their judgment during the full moon phase," she points out. "Or, on the other hand, make them less attentive to psychological problems that surface during the remainder of the month."

The more interesting aspects that came out of the study was that researchers discovered panic attacks seemed to happen more often in the spring, while there was a spike in anxiety disorders in the summer months. There was no explanation provided for these trends.