Circadian rhythms are recurring cycles displaying periods of nearly twenty-four hours, which are present in a range of behavioural, physiological and cognitive processes (Buttgereit, Smolen, Coogan, & Cajochen, 2015). Circadian rhythms interact with homeostatic sleep pressure to shape the timing of sleep (Borbély, Daan, Wirz-Justice, & Deboer, 2016). An important manifestation of these circadian traits in human behaviour is chronotype, reflecting the tendency to structure daily activities, including sleep-wake times, according to the underpinning circadian clock (Roenneberg, Wirz-Justice, & Merrow, 2003). Chronotype is also associated with psychological domains, including personality, impulsivity and psychopathology (Li et al., 2018). Furthermore, chronotype is associated with optimal timing of daily performance in a number of cognitive tasks, with a synchrony effect existing between time of testing and chronotype for many cognitive domains (such that late chronotypes perform better later in the day, early chronotypes earlier in the day; Schmidt, Collette, Cajochen, & Peigneux, 2007). Heritability of chronotype is estimated at approximately 50% and recent genome-wide studies have identified a number of clock and non-clock genes associated with a modest portion of trait variance (Kalmbach et al., 2017). For appropriate entrainment of the circadian clock to environmental zeitgebers, the clock responds to both the zeitgeber timing and intensity to shape chronotype (Roenneberg, Kumar, & Merrow, 2007). Age and sex also profoundly influence chronotype throughout the lifespan (Fischer, Lombardi, Marucci-Wellman, & Roenneberg, 2017). One consequence of a later chronotype is a propensity to experience greater levels of social jetlag (SJL): the mismatch between internal biological time and socially driven behavioural schedules suggested to produce chronic circadian misalignment (Wittmann,