Associations between police lethal force errors, measures of diurnal and reactive cortisol, and mental health
Introduction
Police decision-making outcomes, especially those involving lethal force, have been under great scrutiny in recent years, bolstering the need to further examine and identify biological mechanisms that influence police behavior (Andersen et al., 2020, Baldwin et al., 2022). Very few, small-sample empirical studies have explored the biopsychosocial interactions that contribute to police performance errors, despite the topic urgency and established links between occupational stress and negative physical and mental health outcomes (Andersen et al., 2016, Andersen et al., 2018, Andersen and Gustafsberg, 2016b, Arble et al., 2019, Carleton et al., 2018, Giessing et al., 2019, Giessing et al., 2020, Violanti, 2020). The current study builds upon prior research to provide a more comprehensive examination of police errors in lethal force decision-making as associated with measures of biological (i.e., salivary cortisol), psychological, and occupational stress.
Neuroendocrine processes and the Hypothalamic-Pituitary-Adrenal (HPA) axis are central for maintaining general health and functioning (see O’Connor et al., 2020). Cortisol serves a diurnal and regulatory purpose — the cortisol awakening response (CAR) represents psychological anticipation of the coming day, with more pronounced CAR predicted by higher demands and chronic work-related stress (Fries et al., 2009). Cortisol is also secreted reactively in a dose-response manner to the presentation and cessation of perceived threats (Lovallo, 2016). Chronic stress such as that experienced in the policing occupation creates allostatic load (i.e., body ‘wear and tear’) negatively impacting the function of the HPA axis. As a result, autonomic arousal and cortisol patterns are dysregulated and maladaptive neuroendocrine processes impair one’s ability to respond or adapt to stress (Fries et al., 2009, Clow et al., 2004; Lovallo, 2016). Research with non-specialist populations indicates that allostatic load reduces cognitive and decision-making abilities when an individual is fatigued or threatened, as evidenced by low and irregular cardiovascular arousal profiles or high CAR (Schmitt et al., 2013, Roos et al., 2017, Pruessner et al., 2007). Furthermore, dysregulated cortisol increases risk of physical (e.g., cardiovascular disease, obesity) and psychological (e.g., depression, anxiety, posttraumatic stress disorder (PTSD)) health conditions and performance deficits (Beauchaine and Thayer, 2015, Lehrer et al., 2020, Thayer et al., 2009, O’Connor et al., 2020).
In police and other first responders, routine exposure to occupational stressors (e.g., shiftwork, potentially traumatic encounters) have been linked to increased rates of occupational and posttraumatic stress injuries (PTSI), including mental health conditions such as posttraumatic stress disorder (PTSD), depression, anxiety, suicide, burnout (Carleton et al., 2018, Carleton et al., 2019). These and other findings, based on self-reported measures, have informed priority research that aims to understand the physiological mechanisms underlying PTSI and how they influence health and performance using biological measures (Di Nota et al., 2021, Weiss, 2019). Significant prior research has established a direct link between chronic stress, PTSI, and high and/or dysregulated cortisol in the general population (Steptoe and Serwinski, 2016, Thomas et al., 2012, Pruessner et al., 2003, Dedovic et al., 2010) and among police (Violanti et al., 2017, Planche et al., 2019, McCanlies et al., 2020, Giessing et al., 2020, Zhang et al., 2020). However, less is known about the relationships between self-reported (i.e., psychological) and biological (e.g., neuroendocrine measures) stress and police performance (e.g., lethal force decision-making) (Regehr et al., 2008, Verhage et al., 2018; for reviews see Di Nota and Huhta, 2019; Fermino et al., 2018).
A review of the health literature shows that cortisol secretion from increased occupational stress in police may impact fine motor skills needed for effective lethal force behaviors, such as muscle tension, reach accuracy, blink frequency, and shooting postures (Anderson et al., 2019). Direct evidence linking stress physiology and operational performance in police show strong associations between increased heart rate and/or reactive cortisol and increased errors in lethal force decision-making (Baldwin et al., 2022, Di Nota and Huhta, 2019). Performance deficits may be further exacerbated by the compounded influence of cortisol and PTSI symptoms, which are modulated by occupational exposures in police subspecialties like frontline constables or elite tactical unit members (Planche et al., 2019). In a 3-week N-of-1 field study, Giessing et al. (2020) observed that neither diurnal nor reactive cortisol following critical incidents (CIs) were associated with perceived stress. However, the authors did caution that biological and psychological dysregulation may negatively impact operational police performance and health, and recommended research such as what is presented in the current study to be completed.
The current study builds on prior research to investigate the direct impact of biological (i.e., diurnal (CAR) and reactive cortisol) and psychosocial measures of stress on lethal force decision-making in police. We address prior study limitations posed by small sample sizes and inconsistent outcome measures by evaluating a multi-faceted set of police samples and data using biomarkers of CAR and reactive cortisol in response to ecologically valid operational police encounters.
The current paper explored three aims. Specifically, the associations between: 1) diurnal cortisol (CAR) and lethal force errors, 2) reactive cortisol (pre-CI and change in cortisol across CI, ΔCI) and lethal force errors, and 3) self-reported psychosocial stress symptoms and lethal force errors among frontline and tactical officers.
Section snippets
Materials and methods
Four separate police samples from previously published studies (Andersen et al., 2016; Andersen and Gustafsberg, 2016b; Andersen et al., 2018) were compiled into two participant groups by occupational subspecialty (tactical or frontline). Each of the original four police samples were studied with slightly different aims and methods, with cortisol sampling and analyzes consistent across samples and described previously (Planche et al., 2019). However, the current study evaluated diurnal cortisol
Biological variables of stress and lethal force
To evaluate the associations between biological variables of stress and lethal force errors among frontline and tactical officers (aim 1 and 2), binary logistic regression models were run. CAR significantly predicted lethal force errors (β = 0.06, SE = 0.03, z = 2.24, p = 0.03, AIC = 113.33). Individuals with higher CAR had 6.45% (OR = 1.06, CI95 = 1.01, 1.12) increased odds of committing a lethal force error (see Fig. 1a). However, outliers imposing significant influence on the results were
Discussion
A growing number of cross-disciplinary investigations have attempted to identify precursors of lethal force errors by police, which cause significant personal and societal suffering. Despite demands for answers as to why police lethal force errors occur, the current empirical investigation supports that those answers are complex, and that further analysis of nuanced physiological, personal (i.e., psychosocial), situational, and environmental factors of each case are warranted. The present study
Conclusions
To address urgent issues in police use of force research and practice, timely research that elucidates the impact of stress factors on operational police performance is imperative. While the current study provided novel evidence of significant relationships among biological and psychosocial measures of stress, these outcomes may be too nuanced to predict behavioral errors during acutely stressful encounters, including those that require lethal force decisions. The collection of cortisol is
Funding
Funding of this project was provided by a grant from the Government of Ontario Ministry of Labour (ROP 15-R-021), which funded data collection and open access publishing. However, the Ministry had no other involvement in the conceptualization, design, analysis, decision to publish, or preparation of this manuscript. JPA is now funded by Canadian Institutes for Health Research (CIHR) Team Grant, Mental Wellness in Public Safety - Police (433650).
CRediT authorship contribution statement
Jennifer Chan: Validation, Formal analysis, Resources, Writing – original draft, Writing – review & editing, Visualization. Paula Di Nota: Validation, Writing – review & editing, Formal analysis. Kyle Planche: Resources, Data curation. Debanjan Borthakur: Visualization. Judith Andersen: Supervision, Project administration, Funding acquisition, Investigation, Conceptualization, Methodology, Writing – review & editing.
Conflict of interest
None of the authors declare a conflict of interest.
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