An analysis of 15 years of national data on suicides and homicides shows that nocturnal wakefulness is associated with death by both suicide and homicide.

Summary: A 15-year analysis of national data reveals that nocturnal wakefulness significantly heightens the risks of death by suicide and homicide. Nearly 19% of suicides and 36% of homicides occur at night, with factors like age, alcohol use, and relationship conflicts contributing. The study, published in the Journal of Clinical Psychiatry, suggests that disrupted sleep impairs rational thought, leading to impulsive behaviors. The findings highlight the need for further research into sleep improvement and nighttime wakefulness reduction to prevent these tragic outcomes.

Key Takeaways:

  • The analysis shows a five-fold greater risk for suicide and an eight-fold greater risk for homicide between 2 am and 3 am.
  • Nocturnal wakefulness, age, alcohol use, and relationship conflicts are significant factors contributing to higher risks of suicide and homicide at night.
  • Researchers say the study underscores the importance of future research on improving sleep and reducing nighttime wakefulness to help prevent suicides and homicides.

A new analysis shows that risks for death by suicide and homicide peak at night, with nocturnal wakefulness, age, alcohol use, and relationship conflicts being especially prevalent as contributing factors.

Nearly 19% of suicides and 36% of homicides occur at night. Suicide and homicide share little in common, but their highly concordant overnight risk patterns suggest a common feature: nocturnal wakefulness.

Impaired Rational Thought

“Disrupted sleep may acutely impair rational thought, which can drive impulsive behaviors in vulnerable individuals,” says first author Andrew Tubbs, MD, PhD, a researcher in the Sleep and Health Research Program at the University of Arizona College of Medicine – Tucson’s Department of Psychiatry, in a release. “Our analysis of 15 years of data across the US showed that there is a five-fold greater risk for suicide and an eight-fold greater risk for homicide between 2 am and 3 am when adjusting for the number of people who are awake and capable of suicide or homicide.”

The paper was published in the Journal of Clinical Psychiatry.

The ‘Mind After Midnight’ Hypothesis

“The fact that these overnight risk patterns apply to both suicide and homicide are striking,” says the study’s senior author Michael Grandner, PhD, an associate professor of psychiatry at the Univeristy of Arizona, director of the Behavioral Sleep Medicine Clinic, and a BIO5 Institute member, in a release. “In our review of more than 78,000 suicides and 50,000 homicides, we can find some insight into why nocturnal wakefulness—what we are calling ‘the mind after midnight’—carries a distinct risk for dysregulated behaviors.” 

The authors’ “mind after midnight” hypothesis proposes that nocturnal wakefulness deteriorates the brain’s complex decision-making functions and reduces rational thinking during a time when negative mood is at its peak, positive mood is at its lowest, and risk/reward processing is distorted. 

Key Findings and Future Research

The findings supported that hypothesis. Nighttime risk was greater among adolescents and young adults, people who were intoxicated with alcohol, and those experiencing current partner conflict, conflict, but not among those who used cannabis or were currently

Individuals aged 15-24 years experienced a three-fold greater nighttime risk for suicide, while there was an unexpected suicide risk among older adults at 6 a.m. Risk for homicide did not vary by age, though young adults accounted for more than half of all homicide victims.

“Few studies have examined time-of-day trends in violent crime,” Tubbs says in a release. “Future studies could clarify what exactly is happening in the brain to predispose people to these sorts of risks and whether evidence-based strategies to improve sleep and reduce nighttime wakefulness can help reduce the risks and prevent these tragic outcomes.” 

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