Is there an association between the lunar phases and hospital admission for different episode types in bipolar disorder? A retrospective study in northern China

The effects of the moon on mental activities remain contentious. Few studies have investigated associations between lunar phases and different types of bipolar disorder (BD) episodes. In the current study, 7,452 patients with BD from three hospitals were enrolled. Patients were divided into two groups on the basis of episode types, and the effects of lunar phase were examined for each type. The cosinor analysis revealed moon-related rhythmicity in admissions for BD in a period of 14.75 days. There were fewer admissions around the new moon and the full moon. There was no significant difference between different groups in acrophase. There was possibly a temporal lag between the onset of BD and hospitalization. Thus, it is too early to draw firm conclusions about the impact of lunar phases on BD. Sleep might be a middle way from moon effect to admissions of BD. These results have implications for future disease prevention strategies and research.