Hurricane Katrina, the worst hurricane to hit the United States for seven decades has left behind it devastation well beyond that of physical damage to property.
The most expensive natural disaster in the country's history, where over half-a-million people were evacuated, has taken it's toll on not just the physical well being of the population of New Orleans and the Mississippi delta region, it has also had a serious effect on the mental health of survivors.
A survey by a Harvard team of researchers, "The Hurricane Katrina Community Advisory Group Survey", has found that the rate of serious mental illness in areas ravaged by the storm has doubled.
They suggest as many as 200,000 people from Alabama, Louisiana and Mississippi are at risk of serious mental illness as a result of Katrina, and a third are suffering from post-traumatic stress syndrome and two thirds from depression.
The area of the disaster encompassed almost 90,000 square miles, equivalent in size to Britain; 100 people are still missing.
The study's lead researcher Ronald Kessler, says although the rate of serious mental illness in areas devastated by the storm doubled, suicidal urges fell because survivors bonded with each other and forged stronger ties with loved ones and their community.
The Harvard-led study is the biggest mental health study following Hurricane Katrina which killed around 1,500 people along the Gulf Coast.
The survey shows that 15 percent of 1,043 survivors were diagnosed with a serious mental illness five to eight months after the storm; this compares to 6.1% before the hurricane, and 19.9% had mild-moderate mental illness, compared to 9.7% before the hurricane.
As many as 85 percent of the survivors were in dire financial straits with loss of income and housing.
The survey indicates that more than a third endured extreme physical adversity after Katrina struck and 23 percent encountered extreme psychological adversity.