Aggression and Lost Sleep: A Daylight Saving Time Natural Experiment

• In Event: Reduced Sleep as a Risk Factor for Antisocial and Criminal Behavior

Abstract

Background. The purpose of this study was to test the effect of a mild change in sleep on assault rates using the exogenous shock provided by the switches to and from Daylight Saving Time (DST).

Methods. Using NIBRS data and city-reported data from five major cities, we calculated the difference in assault rates on the Monday immediately following DST as compared to the Monday a week later using a Poisson Quasi Maximum Likelihood Estimator model. The same analyses were performed to examine the effects of the return to standard time.

Results. There were 3% fewer (95% CI: -4.3%, -1.6%; p < 0.0001) assaults immediately following DST, when we lose an hour, as compared to a week later. The standard time findings mirrored the DST findings (2.6% rise in assaults, 95% CI: 1.3%, 4.0%, p < 0.0001). Multiple falsification analyses support the DST findings but indicate weaker standard time findings.

Conclusions. This study suggests that mild and short-term changes in sleep may significantly affect rates of assault. Mild fatigue may result in reduced assaults. This study and the mixed findings presented by the experimental literature indicate that measurement variability of both sleep and aggression could result in conflicting findings.

Authors

• Rebecca Umbach, University of Pennsylvania

• Greg Ridegeway, University of Pennsylvania

• Adrian Raine, University of Pennsylvania