Variation in Suicide Occurrence by Time of Day, Day of the Week, Month, and Lunar Phase

Previous studies suggest that suicide occurrence varies by month and day of the week, but not by lunar phase. Variation by time of day has never before been adequately examined; to our knowledge, all previous studies have failed to obtain time-of-death information for a large percentage of cases. We examined suicide occurrence among residents of Sacramento County, CA, during the period from 1925 to 1983. Data were abstracted from coroner's autopsy and investigative reports. In contrast to previous studies, data on time of death were available for a large percentage of cases. 4,190 suicide deaths were identified during the study period. Suicide occurrence varied substantially by time of day; for both sexes and for ages under 65 years, the fewest suicide deaths occurred during the early morning hours, from 0401 to 0800. For recent years of the study, suicides occurred most frequently on Monday for both males and females and for most age groups. Variation by month followed no consistent pattern by gender, age, years of the study, or combinations of these factors. Contrary to popular belief, suicide occurrence did not vary by lunar phase.