Post-traumatic Stress Disorder (PTSD) is a psychiatric condition triggered upon exposure to a traumatic event where someone's life is seriously threatened or injured. The onset varies, and symptoms include recurring nightmares, flashbacks, irritability, isolation, and sleep problems, among others. Combat duty, natural disasters, accidents, rape, kidnapping, and domestic and child abuse are typical events that may lead to development of the anxiety disorder. According to a new study, researchers have discovered a possible biological marker that identifies individuals at risk of developing a stress-related condition.

Lead researcher Charles Marmar, M.D., professor and chair of the Department of Psychiatry at the New York University School of Medicine, and his colleagues examined the stress-hormone levels of police recruits during training to evaluate the relationship between brain activity, reactions to a stressful event, and the development of Post-traumatic Stress Disorder. Experts are unsure why some people develop the condition while others seem to fully recover after harrowing experiences. This study explored reasons for that discrepancy, providing possible biological answers to why some people are more susceptible than others.

Measuring Hormone Levels

Cortisol is a naturally-producing hormone created in the adrenal gland and released in response to stress. Fluctuations in cortisol levels are normal throughout the day, with the highest amounts typically measured in early morning hours. Cortisol cycles are generally consistent, decreasing at night, and rising as part of the body's 'fight-or-flight' response.

The scientists found that among the 296 police officers participating in the three-year study, those whose stress hormone cortisol levels rose the highest after awakening were most likely to experience acute stress disorder symptoms from traumatic experiences witnessed years earlier.

Their findings were based on measurements of the test subjects' cortisol awakening response (CAR), which refers to the difference in cortisol levels at waking and 30 minutes later; these levels were measured while the officers' underwent academy training and prior to experiencing any duty-related traumatic experiences. They were then assessed for signs of distress and PTSD symptoms at 12, 24 and 36 month intervals following the start of active duty.

People with Higher Cortisol Levels More Likely to Develop Anxiety Problems

Those with greater CAR levels at training were found to exhibit greater acute stress symptoms, including faster heart and breathing rates, and more peritraumatic dissociation, or dreamlike detachment from traumatic events. Peritraumatic distress is characterized by stress occurring at or near the time of the event, as opposed to post-traumatic stress, which occurs anytime after. Peritraumatic stress and dissociation does not automatically lead to subsequent PTSD, but rather is a potential indicator for future onset of the condition.

The study found that the CAR level is a pre-exposure risk factor for specific stress symptoms among police officers, though Dr. Marmar noted that further research is needed to understand if identification of at-risk individuals via this biological marker could lead to interventions that might mitigate the impact of exposure to trauma.

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