Low quantity and quality of sleep is increasingly thought to be a causal factor in antisocial behavior and aggression (Kamphuis et al. 2012). The evidence surrounding the relationship between sleep and antisocial behavior has been derived primarily from small samples in experimental settings involving significant sleep deprivation (Cote et al. 2013, 2014), and via self-reports of sleep, affect, and antisocial behavior (e.g., Raine and Venables 2017), although there are exceptions, including studies on children using teacher and parent reporters (Chervin et al. 2003; Fallone et al. 2005). This quasi-experimental study uses an exogenous shock to sleep to measure the effects of mild sleep reductions and increases on quantifiable measures of antisocial behavior (i.e., assaults), using a larger and more representative sample than previously studied. We exploit the switch to daylight saving time (DST) in the spring and the return to standard time in the fall as a mild exogenous shock to sleep to test whether even one night of a mild change in sleep affects rates of assault on the Monday after a switch. As noted in more detail below, although the switch occurs early Sunday morning, the literature generally agrees that effects are most acutely felt on Monday, when inflexible business and school hours enforce a specific wake time. As a secondary issue, cross-disciplinary research has called into question the energy-saving premise of the DST policy and revealed significant unintended effects of DST, both negative and positive. Consequently, there is ongoing legislation in several states surrounding the policy (Victor 2016). This study aims to provide more knowledge about a costly outcome (assault), which would be relevant to policy-makers, researchers involved in policing and corrections, and the general public.

Background

Prior research indicates that DST affects quantity and quality of sleep and that changes in sleep can alter physiological pathways that, in turn, affect aggression.

Sleep and antisocial behavior

A relationship has been proposed between poor sleep quality and anger, short-temperedness, delinquency, and impulsive aggression (Catrett and Gaultney 2009; Kamphuis et al. 2012; Lindberg et al. 2003). The research thus far has focused largely on antisocial or psychiatric populations (Ireland and Culpin 2006; Lindberg et al. 2003) and healthy individuals with consistent sleep disturbances (Coulombe et al. 2011; Granö et al. 2008; Gregory and O’Connor 2002) or short-term extreme sleep deprivation (multiple hours) (Christian and Ellis 2011; Cote et al. 2013; Vohs et al. 2010). Despite the varied methodology, subject pools, and operationalization of both sleep and antisocial behavior, a relationship between poor sleep and antisocial behavior has been found in cross-sectional (Kamphuis et al. 2012) and longitudinal studies (Gregory and O’Connor 2002; Raine and Venables 2017), studies of adults (Granö et al. 2008; Shin et al. 2005; Taub 1977; Vaughn et al. 2015), and children and adolescents (Backman et al. 2015; Becker et al. 2015; Catrett and Gaultney 2009; Chervin et al. 2003; Clinkinbeard et al. 2011; Kamphuis et al. 2012; Meijer et al. 2010). It is important to note that many of these studies considered the consequences of long-term poor sleep and were reliant on self-report measures.

Of particular relevance to this study, and as noted by a narrative review (Krizan and Herlache 2016), direct tests of the results of short-term significant sleep deprivation on a number of antisocial outcomes using experimental methods have reported mixed findings. One study (Kahn-Greene et al. 2006) deprived subjects of sleep for 55 hours and then measured aggression and hostility using fill-in-the-response vignettes. They found that subjects were more likely than controls to direct blame and/or hostility towards others, and to be unwilling to alleviate a conflict by accepting the blame (Kahn-Greene et al. 2006). A contradictory study (Cote et al. 2013) observed reduced reactive aggression (as measured by a Point Subtraction Aggression Paradigm task) in sleep-deprived men as compared to controls, and no relationship between sleep deprivation and aggression in women after 33 hours of sleep deprivation. A study by Vohs et al. (2010) examined the effects of sleep deprivation on reactive aggression as measured by volume of noise chosen by the participant to be blasted at their opponent in a game. In reporting null results, they were unable to show support for effects of sleep deprivation on aggression in either direction. Finally, Haack and Mullington (2005) assessed affect every day for 12 days in an experimentally sleep-deprived group and a control group, and found that sleep restriction did result in higher self-reported anger/aggression, but effects were not seen until a few days of consistent sleep restriction. Moreover, effects were reversed upon a single day of sleep recovery. These experimental tests suggest that the consequences of short-term sleep deprivation are still poorly understood, and results may vary significantly by methodology. Because of these experimental findings, we propose competing hypotheses as to the effects of DST and standard time switches (and by extension, a single hour of sleep loss or gain) on rates of assault. That is, for each switch, assault rates on the following Monday could plausibly increase or decrease.

Possible pathways between sleep and aggression

Less sleep, more aggression?

One plausible pathway through which poor sleep may lead to increased antisocial behavior could be through impaired neurocognitive functioning or sleepiness and subsequent low self-control. There is supporting evidence for each of these relationships and for some of the relationships in sequence, even if the entire sequential pathway has not been explicitly tested.

First, studies involving both sleep disordered (Fulda and Schulz 2001) and healthy populations (e.g., Kronholm et al. 2009; Nilsson et al. 2005; Sadeh et al. 2002; Touchette et al. 2007) have linked poor sleep quality to impairment in a number of cognitive functions. Some studies identified regions of interest a priori, and found sleep quality to be associated with cognitive functions that draw specifically from emotion-processing (e.g., Baum et al. 2014; van der Helm et al. 2010) and executive functioning parts of the brain (e.g., Cote et al. 2014; Rossa et al. 2014; Williamson and Feyer 2000).

Second, employing self-control (for example, to inhibit emotional responses stemming from the limbic system) draws on a limited pool of mental resources (namely executive control functions centered in the prefrontal cortex), and when that pool is lessened, for example by sleep, self-control may be impaired until the pool can be replenished (Hagger et al. 2010).

Finally, the last pathway, between low self-control and increased antisocial behavior, has been formalized in the well-supported, seminal Self-Control Theory (Evans et al. 1997; Gottfredson and Hirschi 1990). An inability to regulate one’s impulses and immediate desires has been associated with antisocial behavior and delinquency (Hay 2001), with convergent findings across a number of samples and methodologies (Cheung and Cheung 2008; Gibbs and Giever 1995; Vazsonyi et al. 2001). In short, both psychological and criminological literature has provided supporting evidence for a causal chain that could link poor sleep quantity/quality and antisocial behavior.

Less sleep, less aggression?

In addition to correlational studies suggesting a simple inverse relationship between sleep and aggression, there is some experimental research documenting the opposite relationship—more sleep deprivation resulting in reduced reactive aggression (Cote et al. 2013). Cote et al. (2013) used a sample of 49 undergraduate students and the Point Subtraction Aggression Paradigm to look at the effect of 33 hours of sleep deprivation on aggression. Predictably, the sleep deprivation subjects self-reported more negative mood than the controls. However, when it came to actual behavioral aggression, sleep-deprived women stole at the same rate as the controls, and sleep-deprived men stole less than the controls. Cote et al. (2013) proposed that lessened sleep may result in increased physiological and cognitive responsiveness, but decreased behavioral aggression. Additionally, as sleep deprivation disrupted the relationship between testosterone and reactive aggression in male subjects, Cote et al. (2013) hypothesized that the reduced testosterone in the sleep-deprived subjects may play a role in the observed reduced reactive aggression.

Vohs et al. (2010) also used undergraduate students to examine the effects of 24 hours of sleep deprivation on reactive aggression (operationalized as level of volume blasted at an imaginary opponent as punishment). In explaining unexpected null findings, Vohs et al. (2010) concluded that rather than sleep deprivation causing aggression, it might be methodological issues and the oft-associated self-regulation depletion driving the general consensus in the correlational literature. They also noted the benefits of measuring behavior as opposed to intention, as was seen in earlier experimental studies (Kahn-Greene et al. 2006). It could be that when presented with hypothetical situations, individuals will rely on lay beliefs as to how they, a sleep-deprived person, should and would respond. Indeed, when looking at how healthy individuals deal with a mild decrease in sleep quantity/quality, it may be that, despite an increase in irritability and negative affect, sleepiness and lethargy reduces the likelihood of their acting on their aggressive impulses.

Daylight saving time, sleep, and cognitive functioning

Anticipating significant differences in assault counts as a result of the reduced sleep caused by DST requires first that the shift to DST results in decreased sleep. Previous research conducted on DST supports this core assumption (Barnes and Wagner 2009). Using a large sample from the American Time Use Survey conducted by the Bureau of Labor Statistics, Barnes and Wagner (2009) found DST to be associated with a self-reported decrease of 40 min of sleep from Sunday to Monday. Proposing DST effects on assault also assumes that the amount of sleep lost is enough to affect cognitive functioning and energy. Research surrounding DST does indicate that even the loss of one hour can result in sluggish cognitive functioning as measured by performance on the SAT (Gaski and Sagarin 2011). Employing methods so as to focus on the loss of sleep, specific connections have been drawn between DST and a resulting rise in car accidents (Harrison 2013), stock market losses (Kamstra et al. 2000; Pinegar 2002), work-place injuries (Barnes and Wagner 2009), the workplace use of the internet for personal reasons or “cyberloafing” (Wagner et al. 2012), reduced test scores (Gaski and Sagarin 2011), crime due to changes in ambient lighting (Calandrillo and Buehler 2008; Doleac and Sanders 2015), and even suicide rates (Berk et al. 2008). These studies have demonstrated that the sleep effects of DST are sufficiently strong for these researchers to have statistical power to detect relationships between sleep and a variety of outcome measures. We note that many of these studies have focused on the transition to DST without examining the switch back to standard time. As a result, while the literature suggests that DST (and a loss of one hour of sleep) has an acute negative effect on cognitive functioning, there is less evidence to support the inverse.

Fall shift to standard time and sleep

The popularly held belief is that we lose an hour of sleep in the switch to DST, but gain an hour in the return to standard time in the fall. At least one study using a nationally representative sample partially supports this hypothesis; Barnes and Wagner (2009) found a lesser but still highly significant loss of 40 min associated with the advent of DST. On the other hand, Harrison (2013) notes in a review that there is no strong evidence that the fall shift results in gaining one hour of sleep. This is also supported by Barnes and Wagner (2009), who found a nonsignificant difference in sleep duration after the fall shift. Furthermore, there is evidence that the adjustment back to standard time is easier and completed faster than its DST counterpart (Kantermann et al. 2007). In accordance with a general lack of consensus and literature, we allow for competing hypotheses as to the effect of the switch back to standard time on assaults.

This study

This study uses the exogenous mild shocks of DST to assess the effect of a short-term, and mild, reduction in sleep time on crime. The advantages of this methodology as compared to earlier sleep/antisocial research is that it uses a representative and large sample of the United States, thus looking directly at a real-world outcome of interest, assaults, as opposed to self-reported aggression or simulated antisocial behavior in an experimental setting. Considering that most adults have adjusted their bed and rise times within one week post-switch (Harrison 2013) we expect to see significant effects of the policy on crime isolated on the Monday immediately following switches (as compared to one week post-switch). We note that by focusing on a one-time loss or gain of a single hour, our study diverges from the existing sleep literature. Additionally, our outcome (assaults severe enough to warrant police involvement) is a highly valid measure of aggression, as opposed to laboratory tests employed in previous studies. Thus, while we do look at a similar cause, sleep, it is difficult to ascertain how our findings will compare to previous findings.

Broadly, our research question is: Does a small change in sleep duration result in increased aggression? Specifically, we will assess whether (1) the rate of assaults is affected by a potential one hour loss of sleep on the Monday following the transition to DST, as compared to the Monday one week after, and whether (2) the rate of assaults is affected by a potential gain of one hour of sleep on the Monday following the return to standard time, as compared to the Monday one week later.