Lately we've been taking a look at crucial concept in the linkage between combat trauma and PTSD -- the "dose-response relationship," which is apparently a more or less linear relationship between more combat trauma experienced and greater chance of developing PTSD. (Earlier blog entries on that topic are linked here and here.)
On the Web, every once in a while you find a gem -- some good and useful material -- in its entirety, and one such "find" is Mary Elizabeth Claire's Ph.D. thesis at Drexel University, available online, called "The Relationship between Critical Incidents, Hostility, and PTSD Symptoms in Police Officers." (The thesis is linked here.)
While we might prefer her thesis to be about combat veterans and PTSD (heh), the reality is, there's quite a bit of overlap or similarity in how police and veterans experience the events that contribute to PTSD, a fact she explains early on, when she writes:
...Although police officers are usually identified with emergency responders, the context in which police officers experience critical incidents is similar to situations experienced by military veterans. Violanti (1996a) identified six areas of police work that are comparable to the experiences of those that served in the Vietnam War: guerilla warfare at home, the identity of the enemy, a continual sense of insecurity, lack of support, witnessing abusive violence, and depersonalization. The first area, guerilla warfare, is similar to the current plight of many police officers. Violanti (1996a) describes police officers as serving in "peacetime combat."
In a segment entitled, Cumulative Effects of Exposure to Critical Incidents, she writes that:
Learning theory suggests that when an individual is exposed to a repeated stimulus, the person either habituates to the stimuli or becomes sensitized to it. When habituation occurs, the individual reduces their responsiveness to the stimuli while sensitization increases and heightens an individual’s responsiveness. Both behaviors are normal responses but how one reacts to a repetitive stimulus often depends on the intensity of the stimulus. A high intensity stimulus generally tends to sensitize a person to the stimulus while habituation occurs when a person is repeatedly exposed to low to moderate stimuli (Barker, 2001).
It is commonly assumed that individuals that encounter traumatic stressors frequently (e.g., police officers, firefighters) habituate to the stimuli, and therefore they are more resistant to the psychological effects of traumatic incidents. However, the opposing view, that the cumulative effect of critical incidents results in more posttraumatic stress symptoms, has become more empirically supported in recent years (Violanti, 1996b). These findings are congruent with the theories of learning since police officers experience high intensity stimuli on a routine basis thus becoming sensitized, not habituated, to the stimuli.
Several studies have investigated the cumulative effect of critical incidents and the development of PTSD symptoms. For example, Stephens and Miller (1998) conducted a study of 527 New Zealand police officers and found a positive relationship between the number of traumatic events and more PTSD symptoms. Trauma experienced prior to joining the police force was not related to PTSD symptoms while trauma experienced after joining the police force was related to more PTSD symptoms.
Martin et al. (1986) reported that 26% of the 56 police officers attending a sensitive crime seminar met criteria for PTSD. Moreover, the authors found PTSD was related to the number of incidents experienced by the officers. The most frequently endorsed symptom "Recurrent and intrusive recollection of the event" was endorsed by 47 % of the police officers. Martin et al. (1986) indicated it is not surprising that this symptom was endorsed most frequently since police officers continually place themselves in situations similar to previous traumatic incidents and have little opportunity to distance themselves from the incident. Likewise, only 11% of the officers reported in engaging in active avoidance of activities. Moreover, sensitization to the repetitive trauma appeared to occur for these police officers as evidenced by the frequent endorsement of hyperarousal and exaggerated startle response.
Mitchell (1999) reported on the qualitative descriptions of 426 officers above the rank of probationer in the United Kingdom. The officers were asked to describe the most memorable critical incident they experienced during their police career. Almost 75% of the descriptions involved death, and almost 33% of the deaths described involved traffic accidents. Although the Lockerbie Disaster and the crash of the RAF Chinook helicopter were frequently reported, traffic accidents were the largest category of memorable critical incidents described. Different occupational groups within the police department participated, however, 60% of the traffic incidents described as memorable and distressing were reported by current members of the traffic division. Thus, it appears that these officers did not habituate to the incidents in which they were commonly exposed, but instead became sensitized to such incidents. Additionally, the length of time since the accident ranged from two weeks to 25 years with a mean of 5.6 years, indicating that time did not ameliorate the impact of critical incidents in this sample.
Neylan et al. (2002) investigated the impact of critical incident exposure on the quality of sleep in 747 police officers from New York, New York, and Oakland and San Jose, California. The investigators found that cumulative critical incident exposure was associated with nightmares, a symptom of PTSD. Furthermore, sleep disturbances were strongly related to PTSD symptomatology and general psychopathology.
Sleep disturbances and how they contribute to PTSD is another well-deserved treatment that we'll have to leave, though, for another time...
