People who experienced stressful life events in the past have higher chances of developing post-traumatic stress disorder (PTSD) or major depressive disorder (MDD). The study, published in the British Journal of Psychiatry, focused on over 1,000 Chileans ravaged by a powerful earthquake and tsunami in February 2010. The earthquake, considered one of the most powerful earthquakes to hit Chile, took more than 500 lives and displaced 800,000 others.
The study used data gathered in 10 cities of Concepcion and Talcahuano, where thousands participated in a cohort study called “PREDICT investigation.” PREDICT focused on predicting the mental health outcomes among primary care patients. While PREDICT was winding up, the earthquake struck Chile, damaging most parts of Concepcion and Talcahuano. Talcahuano, in particular, was hit by a tsunami.
One year after the tragedy, the study identified 1,160 participants who had completed the pre-disaster assessment in PREDICT in 2003 and the post-disaster assessment in 2011. All participants did not have a history of PTSD or MDD. Based on the analysis of the data, the researchers found that 9.1 percent of the participants had developed PTSD, while 14.4 percent were diagnosed with MDD.
The study also revealed that the risk of developing PTSD and MDD tends to be higher among people who have experienced multiple pre-disaster stressors. The researchers said these stressors increase “stress sensitization,” which makes a person vulnerable to negative consequences in the event of another disaster stressor in the future.