Two years before Hurricane Katrina devastated New Orleans, killing 1,800 people and destroying more than 60% of the city’s housing stock, a group of researchers embarked on what was then an average academic study designed to improve the educational performance of about 1,000 low-income parents enrolled at two community colleges in the city.

The storm disrupted the researchers’ entire study but proved to have a silver lining: Their initial survey was suddenly incredibly valuable for an entirely different purpose. If the researchers, based at several universities around the country, could get in touch with everyone again, they’d have something relatively rare in social science research: A before and after comparison of how people respond to the worst and most unpredictable kinds of disasters.

The Resilience in Survivors of Katrina (“RISK”) Project was born, and the researchers ended up tracking down about 70% of their initial cohort twice: one year after the disaster and again after four years. They conducted the same surveys again, also adding questions about how the hurricane had affected their lives. In the years since these surveys, the RISK project has published dozens of studies that compare the pre- and post-Katrina results on topics ranging from post-traumatic stress, child outcomes, residential mobility, and mental health.

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One of the intriguing studies to come out of the work was published recently in the Journal of Happiness Studies. It looked at what you’d expect: The pre- and post-disaster levels of happiness among 491 of the survey participants, all women. It honed in on how they answered the survey question, “If you were to consider your life in general these days, how happy or unhappy would you say you are?”

The results, according Rocio Calvo, an assistant professor at Boston College’s School of Social Work and the lead researcher on the happiness study, were encouraging and surprising. Even only one year after the storm, almost 89% of women remained in the “somewhat happy” or “very happy” categories, though there was a drop in happiness on average. However, by four years after the storm, almost all of the respondents had gone back to their pre-storm happiness levels. “I think individuals are more resilient than they are given credit for,” she says.

This is amazing to think about. These are already vulnerable women who went through major stress because of Katrina–85% of their homes were seriously damaged and almost one-third had lost a family member or close friend. On average, they experienced at least three major stress factors during the storm, such as no medical care for themselves or a loved one or no food to eat.

There was one exception: 38 women who continued to have lower levels of happiness even four years after the storm. They were more likely to be living on their own after the storm and reported consistently lower levels of perceived support from their communities.