Despite the widespread belief that the moon impacts peoples’ mental health and subsequently psychiatric treatment, this study provides no evidence of our celestial neighbour influence

Is it the moon? Effects of the lunar cycle on psychiatric admissions, discharges and length of stay. Gupta Rahula, Nolan Daniele R., Bux Donald A., Schneeberger Andres R. Swiss Med Wkly. 2019;149:w20070. Apr 23 2019, https://doi.org/10.4414/smw.2019.20070

Summary
BACKGROUND: There is an ongoing debate concerning the connection between lunar cycle and psychiatric illness.

AIMS OF THE STUDY: The purpose of the present study was to evaluate the rates of admission to and discharge from psychiatric inpatient treatment, as well as the length of stay, in relation to the lunar cycle, including 20 different categories of phases of the moon.

METHODS: The data of 17,966 cases of people treated in an inpatient setting were analysed. Routine clinical data and data about admission and discharge were used. The lunar calendar was obtained from the website of the US Naval Observatory and was used to calculate the dates of the full moon according to the geographic location of the clinics. The clinics are located in the Canton Grisons in Switzerland. The following phases of the moon throughout the lunar cycle were defined: (a) full moon, (b) quarter waxing moon, (c) new moon, and (d) quarter waning moon. In addition, we coded one day and two days preceding every lunar phase as well as the two days following the respective phases of the moon.

RESULTS: The lunar cycles showed no connection with either admission or discharge rates of psychiatric inpatients, nor was there a relationship with the length of stay.

CONCLUSIONS: Despite the widespread belief that the moon impacts peoples’ mental health and subsequently psychiatric treatment, this study provides no evidence that our celestial neighbour influences our mental well-being.

Keywords: psychiatric illness, inpatient, hospitalisation, phases of the moon, full moon

Introduction

The belief that the moon influences human lives, emotions, and welfare is deeply anchored in human history, dating back to the ancient cultures of Assyria, Babylonia and Egypt [1, 2]. Medieval European mythology and superstition held that humans were transformed into werewolves or vampires under the influence of a full moon [3]. The antiquated and potentially offensive colloquial word “lunatic” derives from the Latin lunaticus (originally derived from Luna – moon), a term that originally referred mainly to epilepsy and madness, because those diseases were at one time thought to be caused by the moon [1].

To date, there is an ongoing debate concerning the connection between lunar cycle and psychiatric illness [4, 5]. The literature presents conflicting results, with the majority of studies showing no relationship between lunar cycle and either psychiatric admissions or emergency evaluations [6–9], psychiatric inpatient admissions [10], use of community psychiatry services [11, 12], violent behaviour [13–17], suicide [18, 19], or sleep disturbances [20, 21]. However, some studies do show relationships between the lunar cycle various psychiatric phenomena. For example, in a study of 17 healthy individuals Cajochen et al. [22] demonstrated under laboratory conditions that around the full moon, electroencephalogram (EEG) delta activity during non-REM sleep (an indicator of deep sleep) decreased by 30%, time to fall asleep increased by 5 minutes, and EEG-assessed total sleep duration was reduced by 20 minutes. These results presented a possible explanation for morning fatigue associated with a full moon [23]. In a prospective study involving 91 psychiatric inpatients, Calver et al. [4] observed an increase of violent and acute behavioural disturbances during the full moon among patients with severe forms of behavioural disturbance at admission. Another study, focused on gender differences regarding distress phone calls, showed that distress calls by women were more strongly linked to the lunar month than were those by men [24]. Family practitioners have also found a correlation between general practice consultation and the lunar cycle [25]. A large prospective case series of 2281 patients similarly showed an increase in frequency of outpatient psychiatric visits for non-affective psychosis during the full moon [26].

Parmar et al. [5] highlighted the importance of a clear operationalisation of the stages of the lunar cycle for scientific study; in their work, they observed significantly different outcomes regarding psychiatric emergency department presentations during different phases of the moon. Other authors have postulated associations, not only with the full moon, but also different lunar phases, showing sudden changes on the day of the full moon including crisis calls, suicide, and psychiatric admission rates as well as significant differences between the quarter waning and quarter waxing moon, including increases in homicides and crisis calls [27]. The authors presented positive findings regarding the relationship between lunar cycles and psychopathology, violence and admission to psychiatric institutions, highlighting the importance of using a more detailed approach than just the full moon. In addition, they suggest analyses should be stratified by gender and diagnostic categories.