POLICE IN-ACTION: The role of freeze-fight-flight in posttraumatic stress symptoms

Police officers are trained to deal with acute threat and to control their
automatic action tendencies in order to optimize adequate response capacity. In
stressful situations, however, most people tend to fall back on primary *freeze-
fight-flight* (FFF) tendencies and have great difficulty controlling their
actions (Leach, 2004). This forms a major problem for people in high-risk
professions, such as police officers, whose control over automatic action
tendencies is essential for optimal performance during stressful situations
(Nieuwenhuys et al., 2012). The relation between automatic and controlled
emotional behavior has considerable consequences for our society. For instance,
with increasing regularity police officers are confronted with violence, and
with growing frequency they respond to this by drawing their firearms,
enhancing the risk of unintended damage and of violence escalation. For these
reasons, stress-induced lack of control over freeze fight or flight tendencies
forms an increasingly recognized problem in high risk professions. Indeed, over
30% of young, inexperienced police recruits develop stress-related symptoms of
fearful avoidance or aggression after being exposed to a life-threatening
situation (Maguen et al., 2009). Moreover, chronic manifestations of increased
flight as well as fight reactions have been associated with avoidance and
aggressive symptoms in victimized veterans and police officers with full blown
posttraumatic stress disorders (PTSD) (Lenhardt et al., 2012). Avoidance
behavior is considered the major maintaining factor in PTSD. Despite the
largely automatic nature of the response tendencies supporting avoidance and
aggressive behavior, previous research has primarily accounted for these
disorders in terms of cognitive biases involving attention, memory, and belief.
However, a large number of patients suffering from stress-related disorders,
such as PTSD, are resistant to current cognitive and pharmacological therapies,
and it remains unclear whether cognitive biases are so pervasive that they can
influence automatic behaviors in PTSD. The most promising road, in fact, is to
test whether such behaviors can be explained by automatic response tendencies.
It is all the more remarkable that this approach has not been applied to
posttraumatic stress symptoms, given that there is a large body of work on
freeze-fight-flight behavior in animals, which comprises a basic adaptive
mechanism that might account for the persistence of posttraumatic anxiety and
aggression in humans. For these reasons, the main objective of this study is to
determine the role of FFF reactions in the development and maintenance of PTSD
symptomatology.

The main objective of this study is to determine the role of
freeze-fight-flight reactions in the development and maintenance of PTSD
symptomatology.

The study consists of two waves of data assessment. The first assessment wave
takes place before (scan 1; pre-exposure) police recruits make the transition
from the relatively save environment of theoretical training to their first
services in the emergency aid. The second assessment wave takes place after
(scan 2; post-exposure) the police recruits have been exposed to the relative
stressful services in the emergency aid. After completion of data collection we
will be able to prospectively predict trauma-related changes in phenotypic PTSD
symptoms, on the basis of pre-existing FFF markers (i.e., measures on the
behavioral, psychophysiological, neuroendocrinological and MRI levels) assessed
at Scan 1. In addition, we will test whether changes in FFF markers from Scan 1
to Scan 2 relate to PTSD-symptomatology after exposure to aversive events. This
prospective study approach enables us to distinguish predisposing from acquired
abnormalities in FFF reactions to predict PTSD symptomatology after the
experience of aversive events.

During testing, participants will undergo established behavioral tasks and MRI
scans. Some are stress induction and anxiety provocation procedures that may
cause a moderate level of subjective distress. Our lab has extensive previous
experience with these procedures (see e.g., CMO protocol numbers 2010/257,
2011/382 and 2013/551). All procedures described in this protocol are well
established, carry negligible risk, and constitute a minimal burden for the
participants. Young healthy police recruits at the police academy are chosen as
subjects in the study because subsyndromal PTSD-symptoms are highly prevalent
among police officers. Further, the current design has a baseline assessment
when police recruits are still in the relatively safe environment provided by a
police academy training, and a follow-up measurement wave after 12 months of
which 6 months have been spent during armed duty in emergency aid, were they
will be exposed to critical incidents (involving suicide, violence, childhood
abuse, disasters etc) on a regular basis. Consequently, participants only have
to visit the lab twice; once at the beginning of their police education (Scan
1), the other towards the end (Scan 2), with approximately 12 months in
between. No pharmacological or otherwise invasive interventions are applied.