Biological Clocks and Rhythms of Anger and Aggression

Abstract

The body’s internal timekeeping system is an under-recognized but highly influential force in behaviors and emotions including anger and reactive aggression. Predictable cycles or rhythms in behavior are expressed on several different time scales such as circadian (circa diem, or approximately 24-h rhythms) and infradian (exceeding 24 h, such as monthly or seasonal cycles). The circadian timekeeping system underlying rhythmic behaviors in mammals is constituted by a network of clocks distributed throughout the brain and body, the activity of which synchronizes to a central pacemaker, or master clock. Our daily experiences with the external environment including social activity strongly influence the exact timing of this network. In the present review, we examine evidence from a number of species and propose that anger and reactive aggression interact in multiple ways with circadian clocks. Specifically, we argue that: (i) there are predictable rhythms in the expression of aggression and anger; (ii) disruptions of the normal functioning of the circadian system increase the likelihood of aggressive behaviors; and (iii) conversely, chronic expression of anger can disrupt normal rhythmic cycles of physiological activities and create conditions for pathologies such as cardiovascular disease to develop. Taken together, these observations suggest that a comprehensive perspective on anger and reactive aggression must incorporate an understanding of the role of the circadian timing system in these intense affective states.

Are Owls and Larks Different When it Comes to Aggression? Genetics, Neurobiology, and Behavior

“…The finding that Clock expression in the SCN and circadian expression of molecules involved in the stress response were altered in aggressive and impulsive rats supports this notion (Kerman et al, 2012). Data from transgenic mice with mutations affecting clock genes suggest that circadian dysfunction can elicit aggression (Hood and Amir, 2018). For example, knocking out the clock genes reverb alpha (Chung et al, 2014) and clock (Roybal et al, 2007;Coque et al, 2011) increases resident-intruder aggression, and hyperactivity/impulsivity, respectively.…”

“…In theory, the notion that circadian misalignment elicits increased aggression would rely on diurnal differences in aggression. Chronotype differences in aggression have been proposed as evidence that circadian fluctuations influence aggression (Hood and Amir, 2018). The presence of increased verbal and physical aggression in the afternoon in Alzheimer's disease patients has also been suggested as one explanation for diurnal differences in aggression (Coogan et al, 2013;Hood and Amir, 2018).…”

“…Chronotype differences in aggression have been proposed as evidence that circadian fluctuations influence aggression (Hood and Amir, 2018). The presence of increased verbal and physical aggression in the afternoon in Alzheimer's disease patients has also been suggested as one explanation for diurnal differences in aggression (Coogan et al, 2013;Hood and Amir, 2018). However, until now, there has never been a demonstration that aggression is influenced by an endogenously-generated circadian rhythm (Hood and Amir, 2018).…”

“…The presence of increased verbal and physical aggression in the afternoon in Alzheimer's disease patients has also been suggested as one explanation for diurnal differences in aggression (Coogan et al, 2013;Hood and Amir, 2018). However, until now, there has never been a demonstration that aggression is influenced by an endogenously-generated circadian rhythm (Hood and Amir, 2018). For the first time, Todd et al (2018) demonstrated in mice that there is a true circadian rhythm in territorial aggression that persists under constant conditions (without zeitgebers).…”

“…Polymorphisms in circadian genes have been associated with both chronotype and aggression, especially in 5-HT and DA genes, where dysregulation is thought to mediate aggression (Tuinier et al, 1995;Higley et al, 1996;Coccaro et al, 1998;Provençal et al, 2015;da Cunha-Bang et al, 2016). For example, recent GWASs have identified loci near clock genes and those involved in the serotonergic system that highly influence morning or evening preferences (Hu et al, 2016;Jones et al, 2016;Hood and Amir, 2018). However, genetic association studies with aggression and core clock gene polymorphisms have not yet been conducted.…”