Ten years after Hurricane Katrina devastated the city of New Orleans, forcing more than half a million residents to flee, psychologists are investigating the mental and emotional fallout of the natural disaster.
A series of longitudinal studies of Katrina survivors, featured this week in the journal Nature, paint a complicated picture of the storm's repercussions for mental health.
The studies, which were conducted as part of the Resilience in Survivors of Katrina Project, showed that many Katrina survivors experienced mental health issues related to the disaster. But researchers were surprised to observe that a number of survivors also showed remarkable resilience, and even growth, in the wake of trauma.
"The possibility of positive change was so far from our radar screens that not a single question about improvement was included in our first round of post-disaster [data] collection," Dr. Jean Rhodes, a psychologist at the University of Massachusetts in Boston and one of the RISK project's principal investigators, told The Huffington Post. "Yet our data revealed that natural disasters and other traumatic events could be engines of growth, resulting in a kind of spiritual awakening."
Rhodes noted that this growth didn't come easily: A high percentage of survivors struggled with post-traumatic stress disorder and other mental health conditions before going on to experience what is known as post-traumatic growth. Others experienced mental illness related to the disaster that ultimately did not lead to resilience or growth.
The RISK Project, created by Rhodes and a team of psychologists from around the country, came about in an unexpected way. In 2003, the team began collecting data on more than 1,000 low-income parents in New Orleans, to study whether receiving community college scholarships would improve the parents' well-being.
Interrupted when Katrina hit in 2005, the researchers got a rare opportunity to use the data they had already collected -- which included information on economic status, social connections, and physical and mental health -- to track the participants' health after the storm and compare it to their pre-storm baseline.
Since the hurricane, the team has conducted follow-up studies to determine the effects of the trauma on the participants' physical, mental and social well-being.
They found that nearly half of the 392 men and women who took part in the follow-up showed symptoms of PTSD one year after Katrina, while 14 percent suffered from other serious mental illnesses such as depression and psychosis -- double the rate at which they suffered from these conditions before the storm hit.
Other research has corroborated these findings, including one study of storm-affected areas showing that mental illnesses like PTSD and depression tended to get worse following the disaster. That study showed that the percentage of people experiencing suicidal thoughts several months after Katrina had more than doubled by one year after the storm, while rates of PTSD rose from 15 percent to 21 percent in that time period.
What were the most psychologically devastating aspects of the disaster? Threats to one's own physical well-being and the well-being of others were the factors most highly correlated with PTSD and general psychological distress, as well as lack of basic survival needs -- such as food, water and medical care -- and loss of a pet.
However, one study using RISK data, which focused on low-income, unmarried African-American women who survived the storm, found that nearly half of participants could be considered resilient, meaning they experienced an increase in psychological distress after the disaster, but returned to pre-disaster distress levels within three years.
What's more, roughly 30 percent of survivors experienced post-traumatic growth, meaning they felt the experience in some way made them stronger. This growth took the form of improved relationships, greater empathy and compassion, enhanced spirituality, an improved sense of personal strength and the ability to envision new possibilities in life.
Those who had strong support from their families, friends and communities were most likely to show resilience and growth, according to Joy Osofsky, a Louisiana State University psychologist who set up mental health care facilities in New Orleans during the storm's aftermath.
"With support from friends, services providers, mental health support ... we saw a great deal of post-traumatic growth," said Osofsky, who was not involved in the RISK project but has conducted research on psychological well-being in Katrina survivors. "People would share that going through Katrina was devastating; however, they felt they had also learned a lot and because of that experience would be better able to cope with other adversities in their lives."
It's not just individuals who showed remarkable growth in the wake of extreme loss. As several disasters (most recently the Charleston, South Carolina, shooting) have shown, entire communities also are capable of rallying together and rebuilding themselves.
"Communities that have been damaged and even destroyed by a large disaster can learn from it and come out stronger," Rhodes said. "With planning and a post-traumatic growth mindset, societies can harness the shock and loss of a disaster, and use it to fundamentally change for the better."
The RISK project's findings may help psychologists and public health workers identify factors that lead to an increased risk of psychological trauma, and to better treat disaster-related mental illness in the future.
Rhodes added that post-traumatic growth on a societal level is not only possible but also potentially "necessary in the coming years as we face the mounting threat of catastrophic loss from climate change."