Individuals with a history of stressful life events have a higher risk of developing post-traumatic stress disorder (PTSD) and major depressive disorder (MDD), especially after a natural disaster. A study carried out on 1000 participants who faced a powerful earthquake in Chile revealed that the probability of developing PTSD and MDD increased with the number of stressors the participants had encountered.
Students at Brown University conducted the research to challenge the notion that "what does not kill us makes us stronger" by demonstrating that prior stressors can make individuals more susceptible to subsequent stressors. Most people with a history of a traumatic event will not develop PTSD or MDD. However, prior trauma makes them more vulnerable to developing these disorders in their lifetime.
The role of previous trauma is evident in the evaluation of mental health. People with PTSD and MDD may need more extensive services to help them deal with the trauma. The study results indicate the necessity of focusing on the issues of vulnerable groups of people who might not have enough resources to deal with the consequences of prior disasters.