Suicides are more likely to occur between midnight and sunrise, according to a recent study HealthDay reported.

Researchers from the American Academy of Sleep Medicine found that the mean suicide rate per hour was 1.27 percent after midnight, peaking at 16.27 percent between 2 a.m. and 2.59 a.m.  In contrast, the mean suicide rate per hour between 6 a.m. and 11:59 p.m. was 2.13 percent.

"This appears to be the first 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," lead investigator Michael Perlis, director of the Penn Behavioral Sleep Medicine Program at the University of Pennsylvania in Philadelphia, said in in a statement. "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."

When six-hour time blocks were examined, the observed frequency of suicide between midnight and 5:59 a.m. was 3.6 times higher than expected.

For the study, researchers analyzed data from the National Violent Death Reporting System, which provided information 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.

They categorized the time of fatal injury into one-hour bins; the hourly distribution of this data was weighted by the proportion of people awake at each hour and scaled to 100 percent.  More than 35,000 suicides were included in the analysis.

Researchers said an implication of the study is that the treatment of insomnia may be one way to reduce suicide risk. The American Academy of Sleep Medicine reports that about 10 percent of adults have a chronic insomnia disorder lasting at least three months.