**3.1 Police stress**

Police are often the first to arrive to emergencies where they are regularly exposed to dangerous or threatening situations which pose possible harm to their physical and mental health. Previous literature has established that police exhibit stress responses during active duty and in training [26, 27]. Police occupational stress is significantly linked to poorer health, including lower physical and mental health, and higher physician-diagnosed morbidity, cardiovascular disease, and metabolic syndrome [28]. Heightened anticipatory threat anxiety in these high pressure environments can also result in reduced attentional control that influences active performance [29] and decision making tasks [30] (e.g., motor execution, inhibitory control, use-of-force decisions). Because police health significantly impacts their performance and communities, researchers have focused on understanding how models of physiological stress may apply to their operational stress conditions.

While previous research on police diurnal cortisol focused on the effects of factors such as shift-work, posttraumatic stress disorder (PTSD), sleep quality, and cardiovascular disease, there was limited research providing baseline norms for diurnal cortisol patterns as a function of occupational risk. Our research group has addressed an existing gap in the literature by examining diurnal cortisol patterns of police officers from different risk subspecialties, specifically, frontline and tactical police [10]. Frontline police officers' duties include direct interaction with members of the community in response to unlawful acts witnessed while on patrol, or civilian-reported events. As frontline officers are frequently first to arrive to the scene, they also determine if further specialty units are needed to resolve an incident. Specialty units within a police service, such as tactical teams, are equipped with skills, tools, and training to respond to the highest risk incidents that are beyond the capabilities of an average frontline officer (e.g., active shooter events, barricaded suspects, hostage situations); in many police organizations, tactical units are required to first serve as a frontline officer before enrolling in specialized training to obtain and maintain advanced skills for such incidents [31, 32].

The authors' prior work revealed objective evidence that police had higher diurnal cortisol patterns in comparison to the general population, especially within 30 minutes of waking (CAR). Cortisol levels also differed in respect to police subspecialties. Specifically, tactical officers (the highest risk subspecialty) displayed significantly higher CAR in comparison to frontline officers.
