The famous quote from the German philosopher Friedrich Nietzsche, “That which does not kill us makes us stronger,” may not be true after all – at least when it comes to mental health.
Results of a new study show that individuals who have a history of a stressful life events are more likely to develop posttraumatic stress disorder (PTSD) and/or major depressive disorder (MDD) following a major natural disaster than their counterparts who do not have such a history.
The investigation of more than a thousand Chilean residents – all of whom experienced one of the most powerful earthquakes in the country’s history – showed that the odds of developing postdisaster PTSD or MDD increased according to the number of predisaster stressors participants had experienced.
“We’ve learned that Nietzsche was wrong in this case and that the people who have had prior stressful and traumatic histories were more likely to develop PTSD and depression than those with fewer, study investigator , professor of epidemiology at Brown University, Providence, Rhode Island, said in an interview.
The study was published online June 11 in the British Journal of Psychiatry.
Stress inoculation hypothesis
The so-called stress inoculation hypothesis proposes that individuals who experience manageable stressors may be able to better cope with subsequent stressors, inasmuch as such experience affords them opportunities to practice effective coping skills and develop a sense of mastery over stressors.
, particularly with respect to such common mental health disorders as MDD and PTSD. Although less severe day-to-day stressors may be easier to cope with, major trauma can overwhelm an individual’s coping mechanisms.
Findings from previous research have been mixed. Some studiessuggest that prior stressors can increase the risk of developing later psychiatric disorders. On the other hand, previous research has also shown that exposure to prior trauma alone does not predict subsequent PTSD.
Given these contradictions, the investigators wanted to determine whether a history of prior stressors was associated with psychiatric resilience among individuals who had no psychiatric history of MDD or PTSD.
“Only a small minority of people who have experienced a traumatic event go on to develop PTSD or MDD,” said lead author, a psychiatric epidemiologist at the PAHO/WHO Collaborating Center for Research on Psychiatric Epidemiology and Mental Health, Brown University, Providence, R.I.
“So most people are resilient and move on without developing these disorders. But what is unique about this minority of individuals that makes them more susceptible to developing these disorders?” she continued. “It’s one of the most significant questions in the PTSD literature,” she added.
The analysis included data from 10 sites in the Chilean cities of Concepción and Talcahuano that had participated in the PREDICT investigation, a prospective cohort study that sought to predict mental health outcomes among primary care patients.
While the PREDICT study was being conducted, in February 2010, a major earthquake struck the coast of central Chile, killing more than 500 people and displacing 800,000. Concepción and Talcahuano experienced the most damage from the earthquake and its subsequent effects, including a tsunami that ravaged Talcahuano.