Wakefulness in overnight hours significant factor for suicide risk in Australia

Nocturnal wakefulness, particularly in the overnight hours, was shown to be a significant factor for suicide risk among Australians who committed suicide in 2017, according to a study published in the Journal of Clinical Psychiatry.

“Time-of-day as a potential suicide risk factor has been previously explored, with studies producing mixed results,” Darren R. Mansfield, PhD, of the Turner Institute for Brain and Mental Health at the Monash University in Melbourne, Australia, and colleagues wrote.

Mansfield and fellow researchers aimed to examine the times of day for Australian suicide cases, with adjustments for expected sleep patterns, to uncover risk factors for suicide.

The study analyzed information from the Australian National Coronial Information System database for completed suicide during the year 2017 and found 2,808 suicides. Time of suicide for the 1,417 individuals for whom it could be allocated was divided into four segments of 6 hours each across 24 hours, determined from the time an individual was last seen alive until time found.

Prevalence of suicide for each time segment was adjusted for the likelihood of being awake for each segment according to normal sleep-wake patterns published from a large Australian community survey. Observed prevalence of suicide was compared with expected values predicted from likelihood of being awake across each time segment calculated as a standardized incidence ratio.

Results showed that, when compared with expected values, suicides were significantly more likely to occur in the overnight segment (time of occurrence, 2301–0500; standardized incidence ratio=3.93) than in the other three segments. Additionally, there was a corresponding lower-than-expected suicide rate for the segments 1101-1700 (SIR = 0.86) and 1701-2300 (SIR = 0.87). “Our findings support a case for more intensive work to better uncover the causal factors that underpin the association between nocturnal wakefulness and suicide risk,” Mansfield and colleagues wrote.