MINNEAPOLIS—Evidence suggests that suicides are significantly more likely to occur between midnight and 4 am than during the daytime or evening, researchers stated at the 28th Annual Meeting of the Associated Professional Sleep Societies.
The weighted, scaled mean suicide rate per hour was 10.27% after midnight, and the rate peaked at 16.27% between 2 am and 2:59 am. In contrast, the mean suicide rate per hour was 2.13% between 6 am and 11:59 pm. When six-hour time blocks were examined, the observed frequency of suicide between midnight and 5:59 am was 3.6 times higher than expected.
“This appears to be the first [set of] data to suggest that circadian factors may contribute to suicidality and help explain why insomnia is also a risk factor for suicidal ideation and behavior,” said Michael Perlis, PhD, Associate Professor in the Department of Psychiatry and Director of the Penn Behavioral Sleep Medicine Program at the University of Pennsylvania in Philadelphia. “These results suggest that not only are nightmares and insomnia significant risk factors for suicidal ideation and behavior, but just being awake at night may in and of itself be a risk factor for suicide,” he added.
Previous research suggesting that more suicides occur during the day failed to account for the proportion of the population that is awake at each given hour, according to the authors. The current study involved archival analyses of the National Violent Death Reporting System, which provided data for the estimated time of fatal injury, and the American Time Use Survey, which provided an hourly proportion of the American population that is awake. Time of fatal injury was categorized into one-hour segments, and the hourly distribution of these data were weighted by the proportion of people awake at each hour and scaled to 100%. A total of 35,332 suicides were included in the analysis.
An important implication of the study is that the treatment of insomnia may be one way to reduce suicide risk, according to Dr. Perlis. The American Academy of Sleep Medicine reports that approximately 10% of adults have a chronic insomnia disorder that has lasted at least three months.