For the past decade researchers have searched for a biological marker that could indicate if an individual is at risk for a stress-related disorder. A new study on police recruits may finally provide the answer.

Researchers discovered individuals who have the greatest rise in the stress hormone cortisol after waking up were more likely to show acute stress symptoms in response to trauma years later as police officers.

The study, led by Dr. Charles Marmar, is one of the largest to identify a possible method for predicting vulnerability to stress during and after a traumatic event. The results are published in journal Biological Psychiatry.

“This study is significant as a potential indicator in determining when people may exhibit stress symptoms in the future,” said Marmar.

“Few studies have prospectively examined the relationships among pre-exposure hypothalamic-pituitary-adrenal activity, acute stress reactions and post traumatic stress disorder (PTSD). The findings may lead us to new insights on how to identify those who are at a higher risk of PTSD.”

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. The study found the greater CAR during academy training predicted greater peritraumatic dissociation and acute stress disorder symptoms over the first three years of police service.

Two unique stress responses were associated with greater CAR: dissociation — a feeling of dreamlike unreality during the traumatic event — and acute stress disorder symptoms after the event.

Acute stress disorder is characterized by intrusive memories of the event, increased heart rate, faster breathing, and conscious avoidance of thoughts or feelings related to the event.

“This research is just the tip of the iceberg,” said Marmar. “We need additional studies to determine if early identification of these risk factors will result in intervention which could help reduce or minimize the long-term effects of trauma exposure.”

Source: NYU Langone Medical Center/New York University School of Medicine