 Researchers use the registry to study the health effects of the disaster and to develop public health recommendations for future disasters.A 2009 study based on registry data found that posttraumatic stress disorder and asthma were the two most commonly reported conditions among registry participants 5 to 6 years after the disaster.The study found that 19% of adult participants reported new posttraumatic stress symptoms, and 10% of adult participants reported developing new asthma.