Commentary: Are Children Like Werewolves? Full Moon and Its Association with Sleep and Activity Behaviors in an International Sample of Children

A recent article by Chaput and colleagues (1) provides evidence that if a relationship exists between lunar cycle and sleep duration and physical activity in children, its association is rather weak and less-than-meaningful. Using an international sample of 9-to 11-year olds (n = 5812), monitored by accelerometers, Chaput and his team found no relationship between lunar cycle and physical activity, and a minimal effect between lunar cycle and sleep duration (~5 min/night less sleep under full moon vs. new moon). While this relationship has been studied in the past, this is the first time it has been studied among a diverse pediatric sample of this size. The authors' findings are important because they provide further evidence against the notion of a so-called lunar effect, a phenomenon that purports increased violence, crime, and birth-rate, occurring in the full moon phase. While this concept may seem far-fetched to some, to many people it is not. In fact, according to a survey of 325 people (2), 140 (43%) thought that " lunar phenomena could alter personal behavior " [(3), p. 149]. Interestingly, this belief was most popular among the health professionals, including social workers, clinical psychologists, and nurses' aides, surveyed in the sample. A separate survey was consistent with these findings. In an examination of lunar cycle on emergency medicine personnel (n = 50), Danzl (4) found that 80% of the emergency department nurses and 64% of the physicians believed that lunar cycle impacts patients. Among the nurses, 92% found higher stress on lunar shifts and expressed desire for financial compensation. Though these anecdotal findings have been empirically debunked (5–11), the portent of the full moon lingers on. To date, the literature on lunar cycle–sleep relationship has been inconsistent in its findings. Among a sample of adults (n = 205), Della Monica and colleagues (12) found a lunar class × sex interaction, with women with reduced sleep, and men with increased REM sleep, in relation to the full moon phase. A study by Turányi and colleagues (13) found reduced deep sleep and sleep efficiency, occurring at the full moon phase. In contrast, several studies (14, 15) have shown no sleep effect at all, occurring at the full moon phase. And in one of the few studies using children (n = 795), Sjödin and colleagues (16) found longer sleep length and reduced activity, both occurring at the full