Under the Brighton full moon: despite there being no conclusive proof of a link between the full moon and human behaviour, many nurses still put a stressful shift down to the lunar effect. Ann Snelson considers the evidence of such irrational thinking

Evidence of widespread acceptance of the concept that lunar activity can influence behaviour on earth is found in sources from Shakespeare to Darwin. Anecdotal literature which associates such behaviours as pyromania and lycanthropy with lunar influence has no empirical basis (Campbell and Beets 1978). Indeed, very scant evidence which supports the existence of the lunar effect has resulted from the numerous empirical studies that have evaluated its validity through the application of statistical methodology to activities such as suicides and psychiatric admissions (Rotton et al 1983).

Lunacy's association with irrationality was first given medical credence by an 18th century physician, Sir William Blackstone (Oliven 1943).

One reason that an association with science has been sustained is because the concept is accepted by large numbers of healthcare workers and is reported in professional literature (Myers 1995). Abundant anecdotal evidence indicates that belief in the lunar effect is still widely held--for example, Vinson (1999)--which serves to give impetus to further research.

The Belief in Lunar Effect (BILE) test

This nine-item survey instrument, developed by Rotton and Kelly (1985), quantifiably measures the degree to which an individual believes or disbelieves in the lunar effect by adding up their responses to give a BILE score.

For example, a survey of 165 undergraduates showed that 46 per cent believed that people behaved strangely when the moon was full, as measured by the BILE instrument (Rotton and Kelly 1985).

Wilson and Tobacyk's (1989) study on a crisis call centre reported that workers there held a significantly greater belief in the lunar effect than non-crisis call workers when tested using the BILE instrument.

Theories for the belief

Misconceptions concerning the moon

Culver et al (1988) suggest that cognitive biases and misconceptions concerning the moon cause people to believe in the lunar effect. However, holding a belief in the lunar effect has never been shown to be associated with the ability to understand how this effect could be wrought.

The belief as a function of anxiety management Attribution theory states that a belief that occurrence of crises can be predicted provides individuals with feelings of control which reduce anxiety (Kelley 1967). Therefore, the belief that the incidence of crises is correlated with lunar phase provides the worker with a sense of control and alleviates anxiety (Wilson and Tobacyk 1989).

Vance (1995) suggests that adherence to believing in the lunar effect among those working in psychiatry is due to their desire to reduce job-related anxiety created by exposure to random stressful stimuli, such as behavioural outbursts. By associating stressors with salient environmental cues, such as the moon, anxiety diminishes.

Additionally, irrationalities cluster around uncontrollable elements which jeopardise wellbeing and superstitious beliefs offer an explanation that makes such difficulties easier to accept (Vinson 1999).

Illusory correlation

'Illusory correlation' defines the report by observers of the correlation of two classes of events which, in reality, are not correlated at all, or are correlated to a lesser degree or even in the opposite direction than reported (Chapman 1967). Research indicates that people...