Narayan Sastry of the University of Michigan and Mark VanLandingham of Tulane University in New Orleans examined the mental health status of 144 pre-Katrina residents of New Orleans one year after the hurricane.

More than half the study participants were African-American, nearly two-thirds had a high school diploma or less education and nearly 60 percent were unmarried. Nearly three-fourths were employed in the month before the hurricane hit.

The study, presented at the Population Association of America in New Orleans, found African-Americans reported substantially higher rates of serious psychological distress than whites.

Almost one-third of blacks were found to have a high degree of distress, compared to 6 percent of whites. Those with higher incomes and more education were much less likely to experience serious psychological distress, the study said.

"Our findings suggest that severe damage to one's home is a particularly important factor behind socioeconomic disparities in psychological distress, and possibly behind the levels of psychological distress," Sastry said in a statement.