Research finds past stressful experiences do not create resilience to future trauma

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Past stressors sensitize people to future traumas, thereby increasing their chances of developing a mental health disorder, according to a new study by researchers from Brown University and published in the British Journal of Psychiatry.

The researchers examined 1,160 Chileans in 2003 and 2011, both before and after the sixth-most-powerful earthquake on record and subsequent tsunami struck their country in 2010. When the study began in 2003, none of the participants had a history of post-traumatic stress disorder (PTSD) or major depressive disorder (MDD). After the 2010 earthquake, 9.1 percent of the survivors were diagnosed with PTSD and 14.4 percent with MDD­.

The risk of developing these disorders was particularly high among individuals who experienced multiple pre-disaster stressors, such as serious illness or injury, death of a loved one, divorce, unemployment or financial struggles, legal troubles, or loss of a valuable possession. To be at increased risk for post-disaster PTSD relative to those with zero stressors, individuals had to have crossed a "severity threshold" of four or more pre-disaster stressors.

MDD displayed a slightly different pattern: Every pre-disaster stressor, even a single stressor, increased a person's risk of developing post-disaster MDD, and each additional stressor further increased the risk, the researchers said.

The researchers said that overall, both findings suggest that the Chilean disaster survivors who had experienced multiple stressors and traumas were at a greater risk of developing a post-disaster mental health disorder compared to those who had experienced few or no prior stressors.

"We hope that this research will spur interest in the face of the increasing number of natural disasters per year, a major consequence of climate change, such as the devastating earthquake that affected Chile and neighboring countries," said Cristina Fernandez, PhD, MSEd, lead author of the study and a psychiatric epidemiologist. "The immediate global impacts of these catastrophic events on disease, death and the economy are largely well-recognized. Unfortunately, despite a high disease burden, mental illness has thus far not achieved commensurate visibility, policy attention or funding."

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