The study is one of the largest to identify a possible method for predicting vulnerability to stress during and after a traumatic event, said lead author Sabra Inslicht, PhD, a psychologist SFVAMC and an assistant adjunct professor of psychiatry at UCSF.
The results are published in the December, 2011 issue of Biological Psychiatry.
For the longitudinal, prospective study, directed by Charles R. Marmar, MD, of NYU, the researchers measured cortisol levels in 296 police recruits when they awakened, and then 30 minutes later. The difference between the two levels is known as cortisol awakening response, or CAR. After one, two and three years of active service as police officers, the study participants were then assessed for stress reactions in response to duty-related traumatic events.
“When we wake up in the morning, we all have a rise in cortisol as part of the normal awakening process that helps mobilize our body to start the day,” said Inslicht. “In this study, the stronger a recruit’s CAR, the greater the chance they would have stress symptoms years later in response to trauma.”
A stronger CAR predicted two specific stress responses: dissociation – a feeling of dreamlike unreality during the traumatic event – and acute stress disorder (ASD) soon after the event. Symptoms of acute stress disorder include intrusive memories of the event, increased heart rate, faster breathing and conscious avoidance of thoughts or feelings related to the event.
“These are symptoms of post-traumatic stress disorder [PTSD], but limited to a shorter timeframe,” said Inslicht. She noted that a significant number of people with ASD go on to develop PTSD.
However, in the current study, the researchers did not find an association between stronger CAR and PTSD. They attribute this to a number of possible factors: police and other emergency personnel tend to report low levels of PTSD early in their careers; self-selection and rigorous screening before acceptance into the police academy may have resulted in a more resilient study population; and police officers are known to minimize their own stigma-related symptoms.
The authors emphasized in their paper the importance of re-examining the same officers they studied later in their careers and replicating the study in a civilian population in order to establish the generalizability of their findings.
The study results are potentially significant for military recruits, according to Inslicht. “It’s very possible that the same vulnerability that we see in this subset of police officers may help predict which veterans develop stress symptoms after a traumatic event,” she said.
Inslicht cautioned that work is still at a very early stage. “While more research is needed to understand these mechanisms, the ultimate goal would be to develop interventions to prevent and treat some of the stress responses that we see – or at least ways of identifying people who may be at higher risk of PTSD and would thus would benefit from getting interventions earlier on,” she said.
Co-authors of the study are Christian Otte, MD, of Charité University Medical Center, Berlin, Germany; Shannon E. McCaslin, PhD and Brigitte A. Apfel, MD, of SFVAMC and UCSF; Clare Henn-Haase, PsyD, of New York University; Thomas Metzler, MA, of SFVAMC; Rachel Yehuda, MD, of Mount Sinai School of Medicine and James J. Peters VA Medical Center, Bronx, New York; and Thomas C. Neylan, MD, of SFVAMC and UCSF and Charles R. Marmar, MD, of NYU.
The study was supported by funds from the National Institute of Mental Health and the Department of Veterans Affairs, some of which were administered by the Northern California Institute for Research and Education.
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SFVAMC has the largest medical research program in the national VA system, with more than 200 research scientists, all of whom are faculty members at UCSF.
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